🏷

Classifications

Harrison's Part

🔗

Mappings

MONDO

MONDO:0013757 congenital nongoitrous hypothyroidism 6

MONDO:0034216 resistance to thyroid hormone due to a mutation in thyroid hormone receptor alpha

📘

Definitions

3

RTH-alpha biochemical and clinical suspicion criteria

RTH-alpha should be suspected when even mild clinical features of hypothyroidism coexist with high or high-normal free T3, low or low-normal free T4, and a normal TSH, and confirmed by THRA sequencing. Low reverse T3, normocytic or macrocytic anaemia, and a mildly raised creatine kinase - particularly in a child - each independently justify sequencing even when the thyroid panel looks unremarkable.

DIAGNOSTIC_CRITERIA Children and adults under investigation for unexplained hypothyroid features

Inclusion criteria

Clinical features of hypothyroidism, even mild
Free T3 high or high-normal
Free T4 low or low-normal
TSH normal or at most mildly raised
Pathogenic heterozygous THRA variant on sequencing

Show evidence (2 references)

PMID:28527577 SUPPORT Human Clinical

"RTHα should be suspected in subjects with even mild clinical features of hypothyroidism together with high/high-normal (F)T3, low/low-normal (F)T4, and normal TSH."

States the suspicion criteria essentially verbatim.

PMID:32349464 SUPPORT Human Clinical

"In such patients, low reverse T3 levels, normo- or macrocytic anemia or, particularly in children, mildly elevated creatine kinase levels would warrant THRA sequencing."

Supplies the three additional findings that independently warrant sequencing.

Anaemia-based paediatric screening filter for RTH-alpha

A computable case-finding filter applied to children seen in paediatric neurology: complete blood count and thyroid function tests in all, then select those with normocytic or macrocytic anaemia, a normal TSH, free T3 in the upper half of the reference range or high, and free T4 in the lower half of the reference range or low, excluding children with an identified neurological aetiology. Selected children proceed to THRA sequencing. The filter is built entirely from the established biochemical and haematological signature rather than from an unproven mechanism, hence ESTABLISHED_CRITERIA.

PHENOTYPE_ALGORITHM Children attending paediatric neurology with anaemia and no specific neurological aetiology

Inclusion criteria

Attending paediatric neurology with no specific underlying neurological aetiology
Normocytic or macrocytic anaemia on complete blood count
Normal TSH
Free T3 in the upper half of the reference range or high
Free T4 in the lower half of the reference range or low

Show evidence (1 reference)

PMID:38148509 SUPPORT Human Clinical

"normo- or macrocytic anaemia, normal TSH levels, fT3 levels in the upper half of the normal range or high, and fT4 levels in the lower half of the normal range or low"

The laboratory selection criteria of the filter, as operationalized.

fT3/fT4 ratio centile screening in children with developmental delay

Plot the free T3 to free T4 ratio on sex-specific centile charts derived from 23,522 measurements in children and young adults, and treat an outlying ratio as an indication to investigate for a thyroid hormone resistance syndrome - MCT8 deficiency, THRA-related RTH-alpha, or SECISBP2 deficiency. The rationale is mechanistic but the mechanism is established, not hypothesized: each analyte may be within its reference interval while the ratio is not.

PHENOTYPE_ALGORITHM Children and young adults (0-29 years) with developmental delay

Inclusion criteria

Developmental delay under investigation
fT3/fT4 ratio outside the sex-specific reference centiles for age

Show evidence (1 reference)

PMID:39201272 SUPPORT Human Clinical

"we were able to demonstrate a clear separation of patient values for the fT3/fT4 ratio from normal and pathological controls"

The separation result on which the proposed screening use rests, including against a disease control group rather than only healthy children.

👪

Inheritance

1

Autosomal dominant HP:0000006

Heterozygous THRA variants are sufficient to cause disease because the mutant receptor acts dominant-negatively on the wild-type allele rather than merely reducing receptor dose. Both de novo occurrence and parent-to-child transmission are documented; the index cases of 2012 and several later reports were de novo, while a four-member first-degree related kindred sharing p.Ala263Val has been described.

autosomal dominant inheritance

Show evidence (2 references)

PMID:37469961 SUPPORT Human Clinical

"Heterozygous pathogenic variants in THRA are associated with resistance to thyroid hormone alpha (RTHα), causing autosomal dominant nongoitrous congenital hypothyroidism."

States the heterozygous, autosomal dominant mode directly, and is also the clearest published statement that the RTH-alpha phenotype and the "autosomal dominant nongoitrous congenital hypothyroidism" (CHNG6) concept are one disease - the basis for the mondo_mappings decision above.

PMID:22168587 SUPPORT Human Clinical

"a de novo heterozygous nonsense mutation in a gene encoding thyroid hormone receptor alpha (THRA) and generating a mutant protein that inhibits wild-type receptor action in a dominant negative manner"

The index case: a de novo heterozygous variant acting dominant-negatively, which is why one altered allele suffices.

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Discussions and Knowledge Gaps

2

Does levothyroxine improve long-term outcomes in RTH-alpha, and does starting it in adulthood help at all?

KNOWLEDGE GAP OPEN rtha_levothyroxine_outcome_benefit

Attached to

treatments#Levothyroxine

Everything known about treatment benefit in RTH-alpha comes from case series of single-digit size with no control arm and no randomization, in a disorder with fewer than fifty published patients. The largest follow-up study enrolled seven patients from two families. Within that evidence base the short-term biochemical and symptomatic effects are reasonably clear (constipation relieved, creatine kinase lowered, anaemia not), but the questions that matter clinically are not answered: whether final height, adult cognitive outcome or cardiovascular risk differ with treatment, and whether initiating thyroxine in an adult diagnosed late does anything. The untreated adult series raises the possibility that the window is early childhood, since untreated adults had a more pronounced phenotype than patients treated from childhood - but that is a between-cohort comparison, not evidence of effect. The 2024 European Thyroid Association guideline describes the whole family of these disorders as managed on a limited evidence base. This will not be resolved by a trial at this prevalence; a prospective international registry with a common outcome set is the realistic route. One experimental result bears on it directly and cuts both ways. In a low-T3-affinity TR-alpha1 knock-in mouse, anxiety and recognition-memory deficits were rescued by high-dose thyroid hormone given in adulthood, while the locomotor deficit required post-natal treatment and was tied to cerebellar development. If that separation holds in humans, "does adult treatment help" has no single answer - it depends which deficit is asked about, and this entry's observation that IQ improved in every treated child except the one diagnosed at 9.5 years is consistent with a graded rather than an absolute window. The caveat is that the mouse lesion is reduced ligand affinity, not dominant-negative corepressor retention, so hormone dose should work better there than in a patient whose mutant receptor is transcriptionally inert.

Show evidence (4 references)

PMID:37469961 SUPPORT Human Clinical

"However, it is not clear if treatment has beneficial effects if started in adulthood."

States the adult-initiation question as explicitly open.

PMID:26303090 SUPPORT Human Clinical

"The genetic and phenotypic heterogeneity of RTHα and its optimal management remain to be elucidated."

An independent statement that optimal management is unresolved.

PMID:38963712 SUPPORT Other

"managing these rare disorders with a limited evidence base"

The current guideline's own characterization of the evidence base it is built on, which is the honest ceiling on any treatment claim in this entry.

+ 1 more reference

The mouse work shows that preventing NCOR1 recruitment by mutant TR-alpha1 reverses growth, bone and erythroid phenotypes. Is the TR-alpha1-NCOR1 interaction a tractable target in human RTH-alpha, or is the rescue an artifact of a genetic manipulation with no pharmacological counterpart?

HUMAN MODEL MISMATCH OPEN rtha_ncor1_targeting_translational_validity

Attached to

pathophysiology#Persistent Corepressor Occupancy at Thyroid Hormone Response Elements

The evidence here is not absent - it is strong, and it is in a mouse. The Thra1PV/+ by Ncor1-delta-ID cross is the cleanest mechanistic experiment in the field, and it establishes corepressor recruitment as causal rather than correlated. But the intervention is a germline-engineered corepressor that cannot be recruited, present from conception, which is not a drug and has no obvious human equivalent. Two things make the translational question live rather than academic. First, the rescue is explicitly partial even in the mouse. Second, the one finding in this disorder that directly addresses reversibility in the other direction - the cardiac work - found that several heart-rate genes are irreversibly down-regulated and that restoring them required raising T3 in utero, which implies some consequences are developmentally fixed before any postnatal intervention could reach them. A structure-guided ligand analogue, ES08, that dissociates corepressor from mutant TR-alpha more efficiently than T3 is the first candidate with a plausible route to patients, but its in vivo evidence is in zebrafish and its human evidence is in patient-derived cells, not in patients. Recorded as HUMAN_MODEL_MISMATCH rather than KNOWLEDGE_GAP because the model evidence exists and is good; what is unknown is whether it transfers.

Show evidence (3 references)

PMID:23610395 SUPPORT Model Organism

"Therefore, therapies aimed at the TRα1-NCOR1 interaction or its downstream actions could be tested as potential targets in treating TRα1 mutant-mediated hypothyroidism in patients."

The authors propose the interaction as a human target, i.e. they themselves frame this as an untested translational step.

PMID:34871063 SUPPORT In Vitro

"Our observations provide proof of principle for developing synthetic ligands that can relieve transcriptional repression by the mutant TRα-corepressor complex for treatment of RTHα."

Describes the corepressor-dissociating ligand as proof of principle, which is the current ceiling of the translational claim.

PMID:37286550 SUPPORT Model Organism

"Exposure of TRα1 mutant male mice to higher maternal T3 concentrations in utero, restores altered expression and DNA methylation of ion channels, including Ryr2."

Shows that correcting at least one set of consequences required an in utero intervention, which bears directly on whether any therapy given after birth could reach them.

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Pathophysiology

12

THRA Dominant-Negative Receptor Variant

Mechanism confidence: Established

A heterozygous THRA variant, usually in the C-terminal ligand-binding domain, produces a TR-alpha1 protein that has lost ligand-dependent transcriptional activation. Critically, the mutant is not simply inert: it retains DNA binding and retinoid X receptor heterodimerization, and crystal structures show that several mutants devoid of transactivation function still bind T3. The defect is therefore downstream of ligand occupancy, in the conformational change that should convert the receptor from a repressor into an activator.

THRA hgnc:11796

Genetic context THRA hgnc:11796 variant_origin: GERMLINE zygosity: HETEROZYGOUS functional_impact_category: DOMINANT_NEGATIVE

The functional impact is recorded as DOMINANT_NEGATIVE rather than LOSS_OF_FUNCTION or PARTIAL_LOSS_OF_FUNCTION because the mutant receptor inhibits the function of the co-expressed wild-type receptor, which is what makes a heterozygous variant pathogenic and makes the phenotype more severe than THRA haploinsufficiency would be.

TR-alpha1 ligand-dependent nuclear receptor activity GO:0004879 ⇓ LOSS OF FUNCTION

Downstream

Persistent Corepressor Occupancy at Thyroid Hormone Response Elements Because the mutant cannot undergo the T3-induced conformational change that dissociates corepressor, the receptor-corepressor complex remains assembled on target gene promoters.

Sparing of TR-beta-Dependent Tissues and the Pituitary Thyrotroph The lesion is confined to THRA, so TR-beta1 and TR-beta2 are structurally and functionally intact and the tissues that depend on them continue to respond to thyroid hormone normally.

Show evidence (2 references)

PMID:22168587 SUPPORT Human Clinical

"a de novo heterozygous nonsense mutation in a gene encoding thyroid hormone receptor alpha (THRA) and generating a mutant protein that inhibits wild-type receptor action in a dominant negative manner"

The founding observation that the THRA mutant protein inhibits wild-type receptor action, i.e. acts dominant-negatively.

PMID:26303090 SUPPORT Human Clinical

"TR binds preferentially to regulatory DNA sequences (thyroid hormone response elements, TREs) in target gene promoters as a heterodimer with the retinoid X receptor (RXR)"

Establishes that the receptor occupies thyroid hormone response elements as an RXR heterodimer, which is the structural basis for a non-functional mutant being able to occupy and silence a promoter rather than simply vacating it.

Persistent Corepressor Occupancy at Thyroid Hormone Response Elements

Mechanism confidence: Established

In the unliganded state a thyroid hormone receptor recruits a corepressor complex containing NCoR or SMRT together with histone deacetylase, which represses target gene transcription; T3 binding normally dissociates this complex and allows coactivator recruitment. The RTH-alpha mutant receptor fails to make that switch, so the repressive complex stays bound. This is the step that distinguishes RTH-alpha from a loss of receptor: the promoter is not merely unactivated, it is actively silenced, and the wild-type receptor on the same response element is held hostage.

repression of T3-responsive target gene transcription GO:0000122 ↑ INCREASED

persistent NCoR/SMRT corepressor binding by mutant TR-alpha1 GO:0001222 ↑ INCREASED

Animal models

Thra1PV/+ dominant-negative TR-alpha1 mouse Mouse recapitulates The defining test: removing the mutant receptor's ability to recruit NCOR1 relieves the phenotype, so the phenotype is a consequence of corepressor recruitment.

Downstream

Transcriptional Silencing of T3 Target Genes in TR-alpha-Expressing Tissues

Show evidence (3 references)

PMID:34871063 SUPPORT In Vitro

"Receptor occupancy by a ligand (T3) promotes the dissociation of this corepressor complex with the relief of transcriptional repression"

States the normal ligand-triggered corepressor dissociation step. It is precisely this step that the RTH-alpha mutant fails to execute, which is what leaves the repressive complex in place on the response element.

PMID:37469961 SUPPORT Human Clinical

"A key molecular pathogenic defect may be persistent co-repressor binding, rather than coactivator recruitment per se."

Attributes the pathogenic defect to persistent corepressor binding specifically, as opposed to a failure of coactivator recruitment.

PMID:23837191 SUPPORT Other

"When T3binds to TRs on positively regulated genes, corepressor proteins are released and replaced by coactivators leading to increased gene transcription."

States the normal corepressor-to-coactivator exchange that the mutant receptor fails to perform. The missing space in "T3binds" is an artifact of the cached full text and is quoted as it appears.

Transcriptional Silencing of T3 Target Genes in TR-alpha-Expressing Tissues

Mechanism confidence: Established

In every cell whose thyroid hormone response is carried mainly by TR-alpha1, T3-responsive genes are held repressed despite normal intracellular hormone. The resulting state is a cell-autonomous hypothyroidism that is refractory to circulating hormone, which is why the phenotype is tissue-patterned rather than generalized.

TR-alpha1-mediated thyroid hormone receptor signaling GO:0002154 ⇓ LOSS OF FUNCTION

Downstream

Impaired Skeletal Maturation

Impaired Gastrointestinal Motility

Impaired Terminal Erythroid Differentiation

Reduced Intrinsic Cardiac Chronotropic Drive

Impaired Skeletal Muscle Maintenance and Regeneration

Impaired Central Nervous System Thyroid Hormone Action

Show evidence (2 references)

PMID:23837191 SUPPORT Other

"TRβ predominates in the hypothalamic-pituitary-thyroid axis, liver, and kidney, whereas TRα transduces much of the thyroid hormone signaling in the heart, skeletal muscle, central nervous system, bone, and intestines"

Names the tissues whose thyroid hormone signaling runs through TR-alpha, which is the set of tissues this node applies to and the reason the downstream consequences are the ones listed.

PMID:34871063 SUPPORT In Vitro

"ES08, which dissociates corepressor from mutant human TRα more efficaciously than T3. ES08 rescues developmental anomalies in a zebrafish model of RTHα"

A pharmacological test of this node: a ligand analogue selected for its ability to dissociate corepressor from the mutant receptor relieves the phenotype, which supports target gene silencing as the operative lesion rather than an unrelated consequence of the variant.

Sparing of TR-beta-Dependent Tissues and the Pituitary Thyrotroph

Mechanism confidence: Established

TR-beta2 carries the thyroid hormone feedback signal in the hypothalamus and pituitary thyrotroph, and TR-beta1 predominates in liver and kidney. None of these is affected by a THRA variant, so the negative feedback loop continues to sense circulating hormone normally and sets TSH at a near-normal level. The intact axis is not a benign detail: it is what removes the laboratory signal that would otherwise announce the disease.

TR-beta-mediated thyroid hormone receptor signaling in the HPT axis GO:0002154

Downstream

Discordant Thyroid Function Profile with Non-Elevated TSH With pituitary feedback intact and peripheral TR-alpha tissues unresponsive, the serum profile settles into the characteristic dissociation rather than the raised TSH of primary hypothyroidism.

Show evidence (1 reference)

PMID:23837191 SUPPORT Other

"TRβ predominates in the hypothalamic-pituitary-thyroid axis, liver, and kidney, whereas TRα transduces much of the thyroid hormone signaling in the heart, skeletal muscle, central nervous system, bone, and intestines"

Establishes that the hypothalamic-pituitary-thyroid axis is TR-beta territory and therefore unaffected by a THRA variant.

Discordant Thyroid Function Profile with Non-Elevated TSH

Mechanism confidence: Established

The biochemical signature is free T3 in the upper half of the reference range or frankly high, free T4 low or in the lower half of the range, a subnormal T4/T3 ratio, low reverse T3, and a TSH that is normal or at most mildly raised. Each component can individually fall inside its reference interval, particularly in adults, so the abnormality is often only visible as the ratio.

Downstream

Escape from TSH-Based Newborn Screening and Diagnostic Delay Newborn screening for congenital hypothyroidism is predicated on an elevated TSH. A disorder whose TSH is normal is therefore invisible to it, and ascertainment falls back on clinical suspicion years later.

Show evidence (2 references)

PMID:25670821 SUPPORT Human Clinical

"the thyroid profile showed low free thyroxine (fT4) levels coupled with high free T3 (fT3), leading to an altered T4 : T3 ratio, along with normal thyroid-stimulating hormone levels"

Reports the full discordant profile, including the normal TSH, in a longitudinally characterized multi-family cohort.

PMID:26303090 SUPPORT Human Clinical

"Biochemical abnormalities include low/low-normal T4 and high/high-normal T3 concentrations, a subnormal T4/T3 ratio, variably reduced reverse T3, raised muscle creatine kinase and mild anaemia."

Adds the subnormal T4/T3 ratio and the reduced reverse T3 to the profile, and links them to the raised creatine kinase and anaemia.

Escape from TSH-Based Newborn Screening and Diagnostic Delay

Mechanism confidence: Established

The practical consequence of an intact TR-beta feedback axis is that the disorder is not captured by population newborn screening and is commonly diagnosed only when a child is investigated for developmental delay, short stature or constipation - or, in adults, incidentally through a gene panel run for intellectual disability. Untreated adults show a more pronounced phenotype than patients treated from childhood, so the delay is not neutral.

Show evidence (2 references)

PMID:37469961 SUPPORT Human Clinical

"The delay in diagnosis is probably due to normal thyroid function tests."

Attributes the diagnostic delay specifically to the normal thyroid function tests, in a series of four adults who reached adulthood undiagnosed and untreated.

PMID:24847461 SUPPORT Human Clinical

"the first humans carrying a defect in TRα1 were not suspected of having a THRA gene mutation initially"

Records that even the index patients were not suspected of the diagnosis, illustrating how little the laboratory profile points to it.

Impaired Skeletal Maturation

Mechanism confidence: Established

TR-alpha1 is the receptor through which thyroid hormone drives growth plate chondrocyte maturation and ossification. With T3 target genes silenced, endochondral ossification and bone age lag, the epiphyses are dysgenetic, dentition and fontanelle closure are delayed, and head circumference is relatively increased - the cluster reported clinically as skeletal dysplasia with macrocephaly.

growth plate chondrocyte CL:1000217

endochondral ossification at the growth plate GO:0001958 ↓ DECREASED

Animal models

Thra1PV/+ dominant-negative TR-alpha1 mouse Mouse partially recapitulates Reproduces growth retardation and delayed bone development, both partially reversible by blocking NCOR1 recruitment.

thraa / thrab CRISPR dominant-negative zebrafish Zebrafish partially recapitulates Reproduces severe postlarval growth retardation and identifies suppressed gh1 and igf1 expression as a proximate cause.

Downstream

Short stature

Delayed skeletal maturation

Epiphyseal dysplasia

Macrocephaly

Delayed eruption of teeth

Delayed closure of the anterior fontanelle

Wormian bones

Cranial hyperostosis Grouped with the other cranial findings as part of the same delayed ossification, though the thickened adult calvarium and the childhood wormian bones are opposite-looking consequences of it.

Coarse facial features The round, coarse, flat facies is described in the literature as part of the same skeletal dysplasia, but the steps between impaired thyroid-hormone-driven skeletal maturation and the specific facial morphology are not characterized, hence an indirect link.

Show evidence (2 references)

PMID:26303090 SUPPORT Human Clinical

"Clinical features include dysmorphic facies, skeletal dysplasia (macrocephaly, epiphyseal dysgenesis), growth retardation, constipation, dyspraxia and intellectual deficit."

Groups macrocephaly and epiphyseal dysgenesis together as the skeletal dysplasia of RTH-alpha, which is why this node carries both as downstream consequences rather than splitting them.

PMID:23610395 SUPPORT Model Organism

"The severe retarded growth, infertility, and delayed bone development were partially reverted in Thra1(PV/+) mice expressing NCOR1ΔID."

Shows in vivo that the growth and bone phenotype of a dominant-negative TR-alpha1 mutant is a consequence of corepressor recruitment, since preventing that recruitment partially reverses it.

Impaired Gastrointestinal Motility

Mechanism confidence: Established

The intestine is a TR-alpha-dependent tissue and severe constipation was part of the presenting picture of the very first reported case. The motility defect is measured, not inferred: colonic manometry in RTH-alpha patients shows decreased peristalsis. Mouse models carrying the ThraE403X allele show extensive intestinal molecular abnormality, confirming that TR-alpha1 acts in the gut. What remains unestablished is the cellular locus - enteric neuron versus smooth muscle.

gastrointestinal smooth muscle contraction GO:0014831 ↓ DECREASED

Downstream

Constipation

Show evidence (3 references)

PMID:22168587 SUPPORT Human Clinical

"Here we describe a child with classic features of hypothyroidism (growth retardation, developmental retardation, skeletal dysplasia, and severe constipation) but only borderline-abnormal thyroid hormone levels."

Severe constipation in the index case, alongside near-normal hormone levels, establishing gut involvement as a core feature rather than an incidental one.

PMID:35574030 SUPPORT Model Organism

"A total of 1,189 DEPs were identified, including 603 upregulated and 586 downregulated proteins."

Documents extensive intestinal protein dysregulation in the ThraE403X mouse, supporting the intestine as a site of TR-alpha1 action. It does not by itself demonstrate a motility mechanism - the manometry evidence below does that.

PMID:32349464 SUPPORT Human Clinical

"Decreased peristalsis was also observed by colonic manometry in several cases with RTHα"

A measured human finding of reduced colonic motility, which is what moves this node from an inference off the constipation phenotype to a physiologically observed defect.

Impaired Terminal Erythroid Differentiation

Mechanism confidence: Established

Mutant TR-alpha1 directly represses key erythroid genes, impairing the differentiation potential of erythroid progenitors and terminal erythropoiesis. In primary erythroid progenitors cultured from RTH-alpha patients the defect presents as a shifted balance rather than an outright block: cells differentiate, but more slowly, staying larger and more c-Kit-positive and becoming glycophorin-A-positive later. Notably the degree of abnormality did not track the severity of the underlying TR-alpha defect, and induced differentiation and T3 exposure worked normally - so the lesion is in spontaneous maturation, not in the capacity to mature. The clinical correlate is the normocytic or macrocytic anaemia that is among the most consistent findings in RTH-alpha and, unlike constipation, is not reliably corrected by levothyroxine.

erythroid progenitor cell CL:0000038

terminal erythroid differentiation GO:0030218 ↓ DECREASED

Experimental models

RTH-alpha patient primary erythroid progenitor cell culture PRIMARY CELL CULTURE Patient-derived progenitors reproduce the erythroid maturation defect in human cells of the affected lineage, carrying the patients' own variants.

Animal models

Thra1PV/+ dominant-negative TR-alpha1 mouse Mouse recapitulates TR-alpha1PV directly suppresses key erythroid genes and impairs erythroid progenitor differentiation and terminal erythropoiesis; blocking NCOR1 recruitment corrects both. The corresponding human feature - anaemia in about 77% of reported cases - is one of the commonest findings.

Downstream

Anemia

Show evidence (4 references)

PMID:29273766 SUPPORT Model Organism

"The expression of NCOR1ΔID ameliorated abnormalities in the peripheral blood indices, and corrected the defective differentiation potential of progenitors in the erythroid lineage."

Places the erythroid defect downstream of corepressor recruitment by the mutant receptor: blocking NCOR1 interaction corrects progenitor differentiation.

PMID:32349464 SUPPORT Human Clinical

"In humans, 23 among 30 cases with available data (77%) had anemia, and it has been one of the most common findings in humans with RTHα"

Quantifies the human anaemia frequency across the published case series, confirming that the mouse erythroid finding corresponds to a common human feature.

PMID:28911146 SUPPORT In Vitro

"Inactivating mutations in human TRα affect the balance between proliferation and differentiation of progenitor cells during erythropoiesis, which may contribute to the mild anemia seen in most RTHα patients."

Human evidence for this node, from primary erythroid progenitors of 11 RTH-alpha patients. This matters beyond adding a citation: without it the node rested on mouse data alone, and CLAUDE.md requires that model-organism evidence not be the only support for a human phenotype.

+ 1 more reference

Reduced Intrinsic Cardiac Chronotropic Drive

Mechanism confidence: Established

TR-alpha1 is the predominant receptor isoform in the heart and mediates thyroid hormone's chronotropic effect. In RTH-alpha the resulting bradycardia is intrinsic to the heart rather than autonomically mediated, and in TR-alpha1 mutant mice the pacemaker channels Hcn2 and Hcn4 remain T3-responsive while several other heart-rate ion channel genes are irreversibly down-regulated. This is why thyroxine does not raise heart rate in these patients - a therapeutically important dissociation rather than a curiosity.

cardiac muscle cell CL:0000746

thyroid hormone-dependent regulation of heart rate GO:0002027 ↓ DECREASED

Animal models

TR-alpha1 mutant cardiac telemetry mouse Mouse recapitulates Reproduces the persistent bradycardia and demonstrates it is intrinsic to the heart, matching the clinical observation that thyroxine does not raise heart rate in patients.

Downstream

Bradycardia

Show evidence (1 reference)

PMID:37286550 SUPPORT Human Clinical

"In the heart, TRα1 is the predominant isoform and mediates the known effects of the hormone such as increasing contractility, oxygen consumption, cardiac output as well as heart rate"

Establishes TR-alpha1 as the cardiac isoform carrying the chronotropic signal, so its dominant-negative inhibition predicts a rate defect.

Impaired Skeletal Muscle Maintenance and Regeneration

Mechanism confidence: Established

TR-alpha is the predominant thyroid hormone receptor isoform in skeletal muscle, where it is required for regeneration after injury and for maintaining muscle mass. In the THRA-PV mouse, persistent COUP-TFII expression in myoblasts blocks myogenic differentiation, and silencing COUP-TFII restores it. The corresponding human observation is a raised creatine kinase, which falls on levothyroxine treatment.

skeletal muscle satellite cell CL:0000594

skeletal muscle regeneration after injury GO:0043403 ↓ DECREASED

Animal models

THRA-PV skeletal muscle model Mouse recapitulates Reproduces impaired regeneration after injury and age-associated muscle loss, and identifies a specific transcriptional intermediary.

Downstream

Elevated circulating creatine kinase concentration Recorded as indirect with unknown intermediates because no located source traces the raised creatine kinase in human RTH-alpha to the specific myogenic defect characterized in the mouse; the two are concordant observations about the same tissue rather than a demonstrated causal chain.

Show evidence (2 references)

PMID:33633251 SUPPORT Model Organism

"A mouse model of resistance to thyroid hormone carrying a frame-shift mutation in the THRA gene (THRA-PV) is associated with accelerated skeletal muscle loss with aging and impaired regeneration after injury."

Establishes the muscle phenotype in a dominant-negative THRA mouse: accelerated muscle loss and impaired regeneration.

PMID:33633251 SUPPORT Model Organism

"THRA is the predominant isoform in skeletal muscle and plays an essential role in skeletal muscle regeneration after injury and maintenance of muscle mass with aging"

Supports treating skeletal muscle as a TR-alpha-dependent tissue, which is why a THRA variant affects it.

Impaired Central Nervous System Thyroid Hormone Action

Mechanism confidence: Established

The central nervous system is a major TR-alpha-dependent tissue, and developmental delay is the most frequent presenting problem in infancy: delayed motor and speech milestones in the large majority of reported infants, with intellectual outcome ranging from normal to moderate impairment and correlating with variant class. Adults diagnosed late describe reduced intellectual and learning abilities alongside tiredness and low mood.

central nervous system neuron CL:2000029

TR-alpha1-mediated thyroid hormone signaling in the central nervous system GO:0002154 ⇓ LOSS OF FUNCTION

Animal models

Low-T3-affinity TR-alpha1 knock-in mouse (TH rescue model) Mouse rescues Thyroid hormone rescues part of the CNS phenotype, and the part it rescues depends on when it is given. This is the closest experimental evidence bearing on whether levothyroxine started late can help, which is the open clinical question for this disorder.

Downstream

Global developmental delay

Motor delay

Mild intellectual disability

Delayed speech and language development

Gait ataxia

Seizure Via abnormal development of GABAergic inhibitory interneurons, which is the intermediate the TR-alpha1 mutant mouse work identifies and to which the human epilepsy association is attributed.

Show evidence (2 references)

PMID:32349464 SUPPORT Human Clinical

"In infants with RTHα, delayed milestones for motor and speech abilities are the most common symptoms, noted in 34 among 40 cases (85%)"

Quantifies developmental delay as the commonest infant presentation across the published cases.

PMID:37469961 SUPPORT Human Clinical

"Delayed motor and language development and decreased intellectual and learning abilities were described."

Documents the same neurodevelopmental domain in adults who were never treated, indicating it is not an artifact of early ascertainment.

⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

Referential integrity issues (1):

Source 'treatments#Levothyroxine' (for edge to 'Serum Creatine Kinase') not found in named elements

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Phenotypes

22

Blood 1

Anemia FREQUENT HP:0001903

Show evidence (2 references)

PMID:32349464 SUPPORT Human Clinical

"In humans, 23 among 30 cases with available data (77%) had anemia, and it has been one of the most common findings in humans with RTHα"

Gives the anaemia frequency across published cases.

PMID:36821077 SUPPORT Human Clinical

"Anemia was present in five patients at diagnosis, which resolved in one adult patient but occurred in one child despite treatment"

Shows that anaemia is present at diagnosis and largely persists on levothyroxine, which is why it is not curated as a treatment-responsive feature.

Cardiovascular 1

Bradycardia OCCASIONAL HP:0001662

Show evidence (1 reference)

PMID:32349464 SUPPORT Human Clinical

"Although most of the patients had normal heart rate or blood pressure, some cases were reported to have bradycardia"

Supports OCCASIONAL rather than a higher frequency: most reported patients have a normal heart rate.

Digestive 2

Constipation VERY_FREQUENT HP:0002019

Temporal: CHRONIC

Show evidence (1 reference)

PMID:32349464 SUPPORT Human Clinical

"Independent of age, constipation is one of the most common clinical symptoms in human cases, being reported in 26 among 31 cases with available data (84%)"

Gives the 84% frequency across published cases, supporting the VERY_FREQUENT classification.

Hepatic steatosis HP:0001397

No pathophysiology node is claimed upstream, for the same reason as Hypercholesterolemia: the liver is a TR-beta-dependent tissue and nothing located explains how a THRA variant produces steatosis.

Show evidence (1 reference)

PMID:42301959 SUPPORT Human Clinical

"Additional clinical features included variably present delayed dentition, chronic constipation, and hepatic steatosis."

Documents hepatic steatosis in a THRA kindred, and its own "variably present" wording is why no frequency is assigned.

Head and Neck 6

Macrocephaly FREQUENT HP:0000256

Show evidence (2 references)

PMID:28471274 SUPPORT Human Clinical

"Both individuals exhibited macrocephaly, delayed dentition, and constipation, together with a subnormal T4/triiodothyronine (T3) ratio, low reverse T3 levels, and mild anemia."

Documents macrocephaly in both adolescents of a two-patient genotype-phenotype study, alongside the characteristic biochemistry.

PMID:32349464 SUPPORT Human Clinical

"Macrocephalia is also a common clinical finding (23 among 33 cases with available data, 70%)"

Gives the 70% frequency across published cases.

Delayed eruption of teeth FREQUENT HP:0000684

Show evidence (2 references)

PMID:38148509 SUPPORT Human Clinical

"Known RTH-α patients had significantly lower median height SD score, higher rates of delayed tooth eruption and closure of the anterior fontanelle, lower haemoglobin levels, and higher mean corpuscular volume (MCV) and CK levels as compared to those found without RTH-α."

Delayed tooth eruption discriminated confirmed RTH-alpha patients from screened children without a THRA variant.

PMID:32349464 SUPPORT Human Clinical

"Delayed tooth eruption was detected in eight among 18 children with available data (44%)"

Gives the paediatric frequency behind the FREQUENT classification.

Delayed closure of the anterior fontanelle HP:0001476

Show evidence (1 reference)

PMID:38148509 SUPPORT Human Clinical

"Known RTH-α patients had significantly lower median height SD score, higher rates of delayed tooth eruption and closure of the anterior fontanelle, lower haemoglobin levels, and higher mean corpuscular volume (MCV) and CK levels as compared to those found without RTH-α."

Reports delayed fontanelle closure at a significantly higher rate in confirmed RTH-alpha patients.

Coarse facial features HP:0000280

Show evidence (1 reference)

PMID:25670821 SUPPORT Human Clinical

"a distinct and consistent phenotype of mild hypothyroidism (growth retardation, relatively high birth length and weight, mild-to-moderate mental retardation, mild skeletal dysplasia and constipation), specific facial features (round, somewhat coarse and flat face) and macrocephaly"

Describes the facial phenotype explicitly as round, somewhat coarse and flat, in a six-patient cohort followed for 18 years.

Wormian bones FREQUENT HP:0002645

Show evidence (1 reference)

PMID:32349464 SUPPORT Human Clinical

"Wormian bones in skull sutures were present in 10 among 31 cases with available data (32%)"

Gives the frequency across published cases with skull imaging.

Cranial hyperostosis HP:0004437

A deep-research lead described thickened calvarium together with "increased bone mineral density" as characteristic in adults. The bone-density half does not hold up: the same review reports bone mineral density as normal in the three adult patients in whom it was measured, so only the hyperostosis is curated here.

Show evidence (2 references)

PMID:32349464 SUPPORT Human Clinical

"Skull radiography showed cranial hyperostosis in some patients"

Supports the radiographic finding, and its hedged wording is why no frequency is recorded.

PMID:32349464 REFUTE Human Clinical

"Bone mineral density was reported to be normal in three adult patients"

Refutes the accompanying claim that bone mineral density is increased in adult RTH-alpha. Recorded rather than dropped, because the expectation is a reasonable one and a reader should see that it was checked and failed.

Integument 1

Skin tags OCCASIONAL HP:0010609

Bound to HP:0010609. A deep-research lead offered HP:0010701 for this phenotype; that identifier is Abnormal circulating immunoglobulin concentration, confirmed by direct lookup against ols:hp, and the report's own Term Validation section flagged it. The correct term was found independently.

Show evidence (1 reference)

PMID:32349464 SUPPORT Human Clinical

"Skin tags were present in 21% of cases with RTHα; seven among 33 cases with available data"

Gives the frequency behind the OCCASIONAL classification.

Metabolism 2

Elevated circulating creatine kinase concentration FREQUENT Elevated circulating creatine kinase activity HP:0003236

Show evidence (1 reference)

PMID:26303090 SUPPORT Human Clinical

"Biochemical abnormalities include low/low-normal T4 and high/high-normal T3 concentrations, a subnormal T4/T3 ratio, variably reduced reverse T3, raised muscle creatine kinase and mild anaemia."

Lists raised muscle creatine kinase among the biochemical abnormalities.

Hypercholesterolemia HP:0003124

Show evidence (2 references)

PMID:25670821 SUPPORT Human Clinical

"Laboratory investigations revealed anaemia and slightly elevated cholesterol"

Reports slightly elevated cholesterol in the cohort.

PMID:37469961 SUPPORT Human Clinical

"Other main features were low hemoglobin and high LDL/HDL ratio."

Documents the raised LDL/HDL ratio in untreated adults.

Musculoskeletal 2

Delayed skeletal maturation FREQUENT HP:0002750

Show evidence (1 reference)

PMID:37469961 SUPPORT Human Clinical

"During childhood and adolescence, short stature, short limbs, metacarpals, and phalanges, and delayed bone age maturation were observed."

Records delayed bone age maturation during childhood and adolescence.

Epiphyseal dysplasia HP:0002656

Show evidence (1 reference)

PMID:26303090 SUPPORT Human Clinical

"Clinical features include dysmorphic facies, skeletal dysplasia (macrocephaly, epiphyseal dysgenesis), growth retardation, constipation, dyspraxia and intellectual deficit."

Names epiphyseal dysgenesis as part of the skeletal dysplasia.

Nervous System 6

Global developmental delay VERY_FREQUENT HP:0001263

Show evidence (1 reference)

PMID:32349464 SUPPORT Human Clinical

"In infants with RTHα, delayed milestones for motor and speech abilities are the most common symptoms, noted in 34 among 40 cases (85%)"

Gives the 85% frequency supporting VERY_FREQUENT.

Motor delay HP:0001270

Show evidence (1 reference)

PMID:37469961 SUPPORT Human Clinical

"Delayed motor and language development and decreased intellectual and learning abilities were described."

Records delayed motor development in four untreated adult patients.

Mild intellectual disability HP:0001256

Show evidence (1 reference)

PMID:25670821 SUPPORT Human Clinical

"a distinct and consistent phenotype of mild hypothyroidism (growth retardation, relatively high birth length and weight, mild-to-moderate mental retardation, mild skeletal dysplasia and constipation), specific facial features (round, somewhat coarse and flat face) and macrocephaly"

Describes mild-to-moderate cognitive impairment as part of the consistent phenotype. The source's term "mental retardation" reflects 2015 usage and is quoted unaltered.

Delayed speech and language development FREQUENT HP:0000750

Show evidence (2 references)

PMID:32349464 SUPPORT Human Clinical

"Speech delay and dysarthric or slow speech are significant disabilities and are seen in the majority of cases"

States that speech involvement is seen in the majority and is disabling, which is what distinguishes it from the general developmental delay entry.

PMID:42301959 SUPPORT Human Clinical

"Both sisters exhibited normocytic anemia and delayed language development."

Independent confirmation in a 2026 three-member kindred, alongside the anaemia.

Gait ataxia HP:0002066

Show evidence (1 reference)

PMID:32349464 SUPPORT Human Clinical

"evident motor discoordination including dyspraxia, ataxia, and broad or unstable gait are some of the clinical findings on neurological examination"

Names the motor signs found on examination, which is the basis for curating a gait phenotype distinct from the milestone delay.

Seizure OCCASIONAL HP:0001250

Show evidence (1 reference)

PMID:32349464 SUPPORT Human Clinical

"Seizures after stimulation with light or audio and abnormal evolution of GABAergic neurons in TRα1 mutant mice correlated with epilepsy in human cases"

Records epilepsy in human cases and links it to the GABAergic interneuron defect of the mouse model. Graded HUMAN_CLINICAL because the sentence is a review's statement about the human cases; the mouse half of the same sentence is what the animal_models links cite separately.

Growth 1

Short stature FREQUENT HP:0004322

Show evidence (2 references)

PMID:37469961 SUPPORT Human Clinical

"During childhood and adolescence, short stature, short limbs, metacarpals, and phalanges, and delayed bone age maturation were observed."

Reports short stature with disproportionate short limbs in four untreated adult patients, referencing their childhood and adolescent course.

PMID:32349464 SUPPORT Human Clinical

"Short stature is one of the most common clinical findings in children with RTHα (12 among 20 children with available data, 60%)"

Gives the paediatric frequency across published cases, which is what fixes this at FREQUENT rather than VERY_FREQUENT.

🧬

Genetic Associations

1

THRA

Gene: THRA hgnc:11796 relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (3 references)

PMID:37469961 SUPPORT Human Clinical

"The pathogenic THRA variants described so far are most frequently located in the C-terminal ligand-binding domain (LBD)"

Locates the disease-causing variants in the ligand-binding domain.

PMID:25670821 SUPPORT Human Clinical

"We observed a genotype-phenotype correlation, with milder outcomes for missense mutations and more severe phenotypical effects for truncating mutations."

Establishes the variant-class to severity correlation in a six-patient, five-family cohort followed for 18 years.

PMID:28471274 SUPPORT Human Clinical

"Neither A263V nor L274P mutations exhibited gain or loss of function in the TRα2 background, and no additional phenotype attributable to this was discerned."

Supports confining the mechanistic claim to TR-alpha1 despite THRA encoding both isoforms.

💊

Medical Actions

2

Levothyroxine

Action: levothyroxine pharmacotherapy Ontology label: Pharmacotherapy NCIT:C15986

Agent: levothyroxine CHEBI:18332

Platform: Small molecule

Levothyroxine is the only treatment in routine use and there is no RTH-alpha-specific therapy. It is partial and tissue-selective for the same reason the disorder exists: raising circulating hormone can partly overcome resistance in tissues whose mutant receptor retains some T3 responsiveness, does nothing where the mutant is transcriptionally inert, and has no target to act on in TR-beta tissues that were never resistant. In practice it relieves constipation, lowers creatine kinase, and improves growth, body composition and dyspraxia in some patients, while anaemia commonly persists. Response tracks variant class: in a paired two-patient study the patient carrying the partially responsive A263V mutant improved in growth, body composition, dyspraxia and constipation, while the patient carrying the transcriptionally inert L274P mutant showed no change in growth retardation or constipation. The theoretical worry about inducing thyrotoxicosis in TR-beta tissues is not borne out for heart rate: thyroxine does not raise heart rate in RTH-alpha patients, because the cardiac defect is intrinsic to the heart and is not reversed by hormone given after birth, which is what makes higher dosing tolerable. (In the mouse the relevant gene expression could be restored by raising maternal T3 in utero, so "irreversible" here means irreversible postnatally, not in principle.)

Mechanism Target:

Impaired Gastrointestinal Motility — The most consistent treatment response: constipation was relieved in every patient who had it in a seven-patient cohort treated for a median of 6.7 years.

Show evidence (1 reference)

PMID:36821077 SUPPORT Human Clinical

"Treatment ameliorated constipation in all patients with this complaint"

Reports complete relief of constipation in all affected patients, which is the clearest evidence that this node is drug-reversible.

Impaired Skeletal Muscle Maintenance and Regeneration — Creatine kinase fell significantly relative to the laboratory upper limit over a median 6.7 years of treatment, which is the available in-human pharmacodynamic evidence that the muscle node responds.

Show evidence (1 reference)

PMID:36821077 SUPPORT Human Clinical

"At the final visit, creatine kinase levels relative to the reference upper limit were significantly lower compared to the pre-treatment ratios"

Documents the fall in creatine kinase on treatment.

Impaired Central Nervous System Thyroid Hormone Action — Partial and apparently age-dependent. IQ improved in most treated children, with the exception being the child diagnosed latest, at 9.5 years - which is the practical argument for early ascertainment rather than for the drug.

Show evidence (1 reference)

PMID:36821077 SUPPORT Human Clinical

"Normal mental functions were achieved and IQ scores improved in most children except one (age at diagnosis, 9.5 years)."

Shows cognitive improvement in most treated children and names the exception by age at diagnosis, which is what supports the age-dependence rather than the uniform benefit.

Impaired Skeletal Maturation — Variable and variant-dependent: growth improved in the patient with a partially T3-responsive mutant and was unchanged in the patient with a transcriptionally inert one.

Show evidence (1 reference)

PMID:28471274 SUPPORT Human Clinical

"Following T4 therapy, growth, body composition, dyspraxia, and constipation improved in P1, whereas growth retardation and constipation in P2 were unchanged."

Directly contrasts the growth response between two patients whose mutant receptors differ in residual T3 responsiveness, which is why this edge is curated as variant-dependent rather than as a general benefit.

Reduced Intrinsic Cardiac Chronotropic Drive — Recorded as a treatment target that does NOT respond. Thyroxine does not raise heart rate in RTH-alpha, because several heart-rate ion channel genes are irreversibly down-regulated while the pacemaker channels remain T3-responsive.

Show evidence (1 reference)

PMID:37286550 REFUTE Human Clinical

"Surprisingly, we report that treatment of RTHα patients with thyroxine to overcome tissue hormone resistance does not elevate their heart rate."

Refutes the expectation that levothyroxine corrects, or conversely over-corrects, the cardiac node. Recorded as REFUTE on this edge rather than dropped, because a treatment target that provably does not respond is a substantive finding: it is the reason high-dose thyroxine is tolerable here.

Show evidence (3 references)

PMID:36821077 SUPPORT Human Clinical

"We demonstrated that constipation was ameliorated, neuromotor development of some children was improved, and creatine kinase levels were diminished with levothyroxine treatment in patients with RTHα, while some features including anemia did not resolve."

The single best summary of what levothyroxine does and does not do in this disorder, including the explicit negative for anaemia.

PMID:36821077 SUPPORT Human Clinical

"Resistance to thyroid hormone alpha (RTHα) is a rare entity and has no specific treatment."

States that no disorder-specific treatment exists, which is why levothyroxine is curated as the only therapeutic entry.

PMID:26303090 SUPPORT Human Clinical

"thyroxine therapy reverses some metabolic abnormalities and improves growth, constipation, dyspraxia and wellbeing"

An independent statement of the partial benefit, naming the domains that respond.

Genetic counselling

Action: genetic counseling Ontology label: Genetic Counseling NCIT:C15240

RTH-alpha is autosomal dominant with a 50% transmission risk from an affected parent, and familial kindreds have been identified only after an index case was sequenced - in one series, four first-degree-related adults were diagnosed after a gene panel run on the index patient for intellectual disability. Counselling therefore doubles as a case-finding route for relatives who have reached adulthood undiagnosed.

Show evidence (1 reference)

PMID:37469961 SUPPORT Human Clinical

"We investigated 4 previously untreated Caucasian adult first-degree-related patients with the THRA c.788C > T, p.(Ala263Val) variant identified by a gene panel for intellectual disability in the index patient."

Documents the familial cascade: four related adults were identified only through the index patient's sequencing, which is the concrete yield of counselling and family testing here.

🔬

Biochemical Markers

7

Serum Free Thyroxine (Free T4) (DECREASED)

Reference Ranges

Thyroxine (T4) free [Mass/volume] in Serum or Plasma 0.8–1.8 ng/dL (Children and adults; conventional clinical laboratory interval, assay- and age-dependent.)

Conventional clinical laboratory interval, recorded rather than cited. LOINC:3024-7 was resolved against the NLM Clinical Table Search Service on 2026-09-10; LOINC is not configured in conf/oak_config.yaml, so this code is not covered by just validate-terms.

Show evidence (2 references)

PMID:28527577 SUPPORT Human Clinical

"In addition, serum (F)T3 levels can be high-normal to high, (F)T4 and rT3 levels normal to low, while TSH is normal or mildly raised."

States the free T4 direction (normal to low) within the full discordant profile.

PMID:37469961 SUPPORT Human Clinical

"While thyrotropin (TSH) and free thyroxine (FT4) were within the reference range, free triiodothyronine (FT3) was high. FT4/FT3 ratio and reverse T3 were low."

Shows that free T4 can sit entirely within the reference range in adults, which is the practical reason the single analyte is not diagnostic.

Serum Free Triiodothyronine (Free T3) (INCREASED)

Reference Ranges

Triiodothyronine (T3) Free [Mass/volume] in Serum or Plasma 2.3–4.2 pg/mL (Children and adults; conventional clinical laboratory interval, assay- and age-dependent.)

Conventional clinical laboratory interval, recorded rather than cited. LOINC:3051-0 was resolved against the NLM Clinical Table Search Service on 2026-09-10.

Show evidence (1 reference)

PMID:32349464 SUPPORT Human Clinical

"Free triiodothyronine (T3) levels are in the upper half of normal range or frankly high and free thyroxine (T4) levels are low or in the lower half of normal range."

States both directions and, crucially, that each can remain inside its reference interval.

Serum Thyroid-Stimulating Hormone (TSH) (NORMAL)

Reference Ranges

Thyrotropin [Units/volume] in Serum or Plasma 0.4–4.0 mU/L (Children and adults; conventional clinical laboratory interval, assay-dependent.)

Inappropriately normal TSH for the degree of tissue hypothyroidism (0.4–4.0 mU/L) → Inappropriately normal thyroid-stimulating hormone level

Inappropriately normal TSH for the degree of tissue hypothyroidism: A TSH inside the reference interval in a child with growth retardation, delayed bone age, constipation and anaemia does not exclude a disorder of thyroid hormone action; in RTH-alpha it is the expected result. Reading it as reassurance is the commonest route to diagnostic delay.

Conventional clinical laboratory interval, recorded rather than cited. The RTH-alpha-specific point is not where the interval lies but that patients fall inside it.

Show evidence (1 reference)

PMID:32349464 SUPPORT Human Clinical

"Many symptoms and findings are similar to those seen in primary hypothyroidism. However, thyroid-stimulating hormone levels are normal."

States the dissociation in one sentence: a hypothyroid clinical picture with a normal TSH.

Serum Reverse T3 (DECREASED)

Reference Ranges

Triiodothyronine (T3).reverse [Mass/volume] in Serum or Plasma – (Not specified - the analyte is bound for machine-queryability; no reference interval is asserted.)

Bounds are deliberately omitted. LOINC:3052-8 was resolved against the NLM Clinical Table Search Service on 2026-09-10.

Show evidence (2 references)

PMID:32349464 SUPPORT Human Clinical

"In such patients, low reverse T3 levels, normo- or macrocytic anemia or, particularly in children, mildly elevated creatine kinase levels would warrant THRA sequencing."

Names low reverse T3 as one of three findings that should trigger THRA sequencing.

PMID:26303090 SUPPORT Human Clinical

"Biochemical abnormalities include low/low-normal T4 and high/high-normal T3 concentrations, a subnormal T4/T3 ratio, variably reduced reverse T3, raised muscle creatine kinase and mild anaemia."

Qualifies reverse T3 as variably reduced rather than uniformly low, which is why it is a supporting and not a defining finding.

Free T4 to Free T3 Ratio (DECREASED)

Show evidence (2 references)

PMID:39201272 SUPPORT Human Clinical

"we were able to demonstrate a clear separation of patient values for the fT3/fT4 ratio from normal and pathological controls"

Demonstrates that the ratio separates confirmed thyroid hormone resistance patients from both normal and disease controls, which is the basis for treating it as the discriminating measurement.

PMID:25670821 SUPPORT Human Clinical

"the thyroid profile showed low free thyroxine (fT4) levels coupled with high free T3 (fT3), leading to an altered T4 : T3 ratio, along with normal thyroid-stimulating hormone levels"

Reports the altered T4:T3 ratio as the composite abnormality arising from the two individually unremarkable analytes.

Serum Creatine Kinase (INCREASED)

Pathograph Readouts

Pharmacodynamic Marker Of treatments#Levothyroxine Negative

Creatine kinase expressed as a fraction of the laboratory's reference upper limit fell from a median of 1.3 before treatment to 0.9 at the final visit in a seven-patient cohort treated for a median of 6.7 years.

Show evidence (1 reference)

PMID:36821077 SUPPORT Human Clinical

"At the final visit, creatine kinase levels relative to the reference upper limit were significantly lower compared to the pre-treatment ratios"

Reports the treatment-associated fall in creatine kinase, which is what makes it a pharmacodynamic marker of levothyroxine here.

Reference Ranges

Creatine kinase [Enzymatic activity/volume] in Serum or Plasma – (Not specified - the analyte is bound for machine-queryability; no reference interval is asserted.)

Bounds deliberately omitted. LOINC:2157-6 was resolved against the NLM Clinical Table Search Service on 2026-09-10.

Show evidence (1 reference)

PMID:38148509 SUPPORT Human Clinical

"Known RTH-α patients had significantly lower median height SD score, higher rates of delayed tooth eruption and closure of the anterior fontanelle, lower haemoglobin levels, and higher mean corpuscular volume (MCV) and CK levels as compared to those found without RTH-α."

Shows creatine kinase is significantly higher in confirmed RTH-alpha patients than in biochemically similar children without a THRA variant.

Haemoglobin and Mean Corpuscular Volume (ABNORMAL)

Reference Ranges

Hemoglobin [Mass/volume] in Blood – (Not specified - strongly age-dependent in children; no interval asserted.)

Bounds deliberately omitted. LOINC:718-7 was resolved against the NLM Clinical Table Search Service on 2026-09-10.

MCV [Entitic mean volume] in Red Blood Cells by Automated count – (Not specified - strongly age-dependent in children; no interval asserted.)

Bounds deliberately omitted. LOINC:787-2 was resolved against the NLM Clinical Table Search Service on 2026-09-10.

Show evidence (1 reference)

PMID:38148509 SUPPORT Human Clinical

"normo- or macrocytic anaemia, normal TSH levels, fT3 levels in the upper half of the normal range or high, and fT4 levels in the lower half of the normal range or low"

Specifies the haematological pattern - normocytic or macrocytic, not microcytic - as used in an actual screening filter.

📈

Progression

2

Infancy and early childhood

Presentation is in the first years of life, and almost always for something other than thyroid disease: growth faltering, delayed motor and speech milestones, or severe constipation. Delayed bone age, epiphyseal dysgenesis, wormian bones, delayed dentition and late fontanelle closure are childhood-specific skeletal findings. Newborn screening has already missed the diagnosis by this point, because it is TSH-based.

Show evidence (1 reference)

PMID:32349464 SUPPORT Human Clinical

"In infants with RTHα, delayed milestones for motor and speech abilities are the most common symptoms, noted in 34 among 40 cases (85%)"

Establishes what brings these children to attention, and when.

Adulthood

The phenotype attenuates rather than progresses, which is itself a diagnostic hazard: epiphyseal dysgenesis present in childhood is absent on adult imaging, and the biochemical abnormalities become subtler, so an adult relative of an index case can look near-normal on thyroid function tests. What persists is anaemia, constipation, and the cognitive and motor phenotype; hepatic steatosis and raised LDL/HDL are reported in adults. Untreated adults show a more pronounced phenotype than patients treated from childhood.

Show evidence (2 references)

PMID:32349464 SUPPORT Human Clinical

"the individual clinical picture or laboratory findings becoming less remarkable with age"

States the attenuation directly. This is why the entry treats adult ascertainment as harder than paediatric, not easier.

PMID:42301959 SUPPORT Human Clinical

"This report adds novel insight by documenting intrafamilial variability and age-related attenuation of biochemical abnormalities in a family carrying a previously described THRA variant."

Independent documentation of age-related attenuation, in a kindred where the mother carried the same variant as her affected daughters.

📊

Prevalence

1

Worldwide, published cases

Cases In Literature Ultra Rare

As of the 2021 review of all published cases, 40 affected individuals from 28 families carrying 25 distinct THRA variants had been reported. Counted cases rather than an estimated population prevalence, because no population-based ascertainment exists and the biochemical profile is near-normal, so the published count is a floor rather than an estimate. Orphanet's own epidemiology entry for ORPHA:566231 records a worldwide point prevalence of <1/1,000,000 and 35 reported cases, but the Orphanet bulk XML is not present in this checkout, so no ORPHA snippet is cited here.

Show evidence (1 reference)

PMID:32349464 SUPPORT Human Clinical

"To date, 40 cases (13 adults, 27 children) from 28 different families with 25 different variants inTHRAgene have been published"

Gives the published case count, family count and variant count behind the ULTRA_RARE class. The missing spaces in "inTHRAgene" are an artifact of the cached full text and are reproduced verbatim rather than corrected.

🔀

Differential Diagnoses

3

Conditions with similar clinical presentations that must be differentiated from Resistance to Thyroid Hormone Alpha:

Allan-Herndon-Dudley syndrome (MCT8 deficiency) MONDO:0010354

Overlapping Features The closest biochemical mimic, and the one that matters most because the lesion is in the opposite part of the pathway: MCT8 is a transporter, so hormone cannot reach the cell, whereas in RTH-alpha hormone reaches the cell normally and the receptor cannot act on it. Both produce a discordant thyroid panel with a non-suppressed TSH and neurodevelopmental impairment.

Distinguishing Features

AHDS has markedly elevated T3 with an elevated T3/T4 ratio and prominent peripheral thyrotoxic features - resting tachycardia, progressive weight loss, muscle wasting, failure to thrive. RTH-alpha has only high-normal to mildly raised T3, a subnormal T4/T3 ratio, and bradycardia rather than tachycardia in the minority with a rate abnormality.
AHDS is X-linked and the neurological picture is far more severe - spastic quadriplegia, absent speech, dystonia - whereas RTH-alpha is autosomal dominant with mild-to-moderate impairment.
Reverse T3 is low in both, so it does not separate them. Definitive separation is by sequencing SLC16A2 versus THRA.

Show evidence (3 references)

PMID:39201272 SUPPORT Human Clinical

"individuals with developmental delay and genetically confirmed thyroid hormone resistance, carrying defects in Monocarboxylate Transporter 8 (MCT8), Thyroid Hormone Receptor alpha (THRα), and Selenocysteine Insertion Sequence-Binding Protein 2 (SECISBP2)"

Groups MCT8, THRA and SECISBP2 defects as the differential set reached through the same presenting problem and the same ratio-based screen.

PMID:39132310 SUPPORT Other

"Both RTH- α and MCT8 de ﬁciency may be associated with neurocognitive deﬁcits and developmental delay, however, RTH- α is associated with bradycardia a nd skeletal anomalies, while MCT8 de ﬁciency is associated with tachycardia and failure"

Gives the discriminating pair directly - bradycardia and skeletal anomalies in RTH-alpha against tachycardia and failure to thrive in MCT8 deficiency - which is the first distinguishing feature above. The broken words and ligatures are artifacts of the cached full text and are quoted as they appear.

PMID:39132310 SUPPORT Other

"The only characteristic MCT8-related thyroid hormone alteration that is present within the newborn period is a low reverse T3 (rT3)"

Supports the third distinguishing feature: reverse T3 is low in MCT8 deficiency too, so it cannot be used to separate the two disorders.

Generalized resistance to thyroid hormone (RTH-beta) MONDO:0009043

Overlapping Features The same class of lesion in the other receptor isoform, and biochemically its mirror image. Because TR-beta carries pituitary feedback, a THRB dominant-negative variant breaks the feedback loop and produces elevated free T4 and free T3 with a non-suppressed TSH - the opposite laboratory picture from RTH-alpha, where the loop is intact and TSH is simply normal.

Distinguishing Features

RTH-beta has raised free T4 and free T3 with a non-suppressed TSH; RTH-alpha has low or low-normal free T4, high-normal or high free T3, and a normal TSH. The TSH in RTH-beta is inappropriate for the elevated hormone levels, whereas in RTH-alpha it is simply normal.
RTH-beta commonly presents with goiter and tachycardia; RTH-alpha is nongoitrous and if anything bradycardic.
Separation is by which gene is sequenced - THRB versus THRA.

Show evidence (2 references)

PMID:28527577 SUPPORT Human Clinical

"Patients with mutations in THRB, exhibiting resistance within the hypothalamic-pituitary-thyroid axis with elevated TH and nonsuppressed thyroid-stimulating hormone (TSH) levels, were first described decades ago."

States the RTH-beta biochemical signature - elevated hormone with a non-suppressed TSH - against which the RTH-alpha profile is contrasted.

PMID:32349464 SUPPORT Human Clinical

"The incidence of RTHβ is reported to be approximately 1/40000 and is characterized by goiter, tachycardia, hyperactivity, failure to thrive and cognitive impairments with high serum TH levels, but normal or mildly elevated TSH"

Supplies the clinical half of the separation - goiter and tachycardia in RTH-beta - and incidentally shows RTH-beta is roughly three orders of magnitude commoner than RTH-alpha.

Primary congenital hypothyroidism MONDO:0018612

Overlapping Features The condition RTH-alpha is most often mistaken for clinically and least likely to be confused with biochemically, once a thyroid panel is done. The clinical picture overlaps substantially - growth retardation, developmental delay, constipation, delayed bone age - but congenital hypothyroidism is defined by an elevated TSH, which is what newborn screening detects and what RTH-alpha lacks.

Distinguishing Features

Primary congenital hypothyroidism has an elevated TSH and is detected by newborn screening; RTH-alpha has a normal TSH and is not.
In primary congenital hypothyroidism both free T4 and free T3 are low; in RTH-alpha free T3 is high-normal or high while free T4 is low-normal, giving the subnormal T4/T3 ratio that is absent in hormone deficiency.

Show evidence (1 reference)

PMID:39201272 SUPPORT Human Clinical

"children with congenital hypothyroidism and reduced thyroid hormone production are diagnosed on the basis of elevated plasma TSH levels"

States the TSH-based diagnostic basis for congenital hypothyroidism, which is the axis on which the two are separated.

🧫

Experimental Models

1

RTH-alpha patient primary erythroid progenitor cell culture PRIMARY_CELL_CULTURE

Primary human erythroid progenitor cells expanded from the peripheral blood of 11 RTH-alpha patients carrying seven different inactivating TR-alpha variants (P398R, F397fs406X, C392X, R384H, A382fs388X, A263V, A263S), compared with 11 healthy controls, with maturation tracked by cell number, cell size, staining and flow cytometry over about 14 days of ex vivo expansion. This is the human-tissue counterpart of the Thra1PV/+ mouse erythroid work and the reason the erythroid node does not rest on animal data alone.

Organism

human NCBITaxon:9606

Cell source

Peripheral blood of 11 genotyped RTH-alpha patients and 11 healthy controls

Culture

Ex vivo liquid expansion and differentiation culture of primary human erythroid progenitors

Publication

PMID:28911146

Pathograph links

Impaired Terminal Erythroid Differentiation partially recapitulates fidelity: high observes: cellular Patient-derived progenitors reproduce the erythroid maturation defect in human cells of the affected lineage, carrying the patients' own variants.

Limitations: PARTIALLY_RECAPITULATES rather than RECAPITULATES because the defect appears only in spontaneous differentiation: induced differentiation and T3 response were comparable to controls, so the culture does not reproduce a general inability to mature. The abnormality also did not correlate with the severity of the underlying TR-alpha defect, which means the system does not report genotype-phenotype gradation. Anaemia itself is an organism-level outcome and is not observed here.

Readouts

Cell size and c-Kit positivity during spontaneous differentiation

Direction: INCREASED

Interpretation: Patient-derived progenitors stayed larger and more c-Kit-positive, i.e. held in a proliferative rather than maturing state.

Show evidence (1 reference)

PMID:28911146 SUPPORT In Vitro

"During spontaneous differentiation, RTHα-derived HEPs were larger, more positive for c-Kit (a proliferation marker), and less positive for glycophorin A (a differentiation marker)."

The measured proliferation-marker and size readout.

Rate of spontaneous erythroid differentiation

Direction: DECREASED

Interpretation: Patient-derived progenitors differentiated more slowly than controls over the same ex vivo period.

Show evidence (1 reference)

PMID:28911146 SUPPORT In Vitro

"After ∼14 days of ex vivo expansion, both control and patient-derived progenitors differentiated spontaneously. However, RTHα-derived cells differentiated more slowly."

The rate readout, including that differentiation still occurred.

Show evidence (1 reference)

PMID:28911146 SUPPORT In Vitro

"Cultures of primary human erythroid progenitor cells (HEPs), from peripheral blood of RTHα patients (n = 11)"

Establishes that the model is human, patient-derived, and of the affected lineage, which is what makes it informative for this node.

Recorded under experimental_models rather than animal_models because it is a non-animal human cell system, per the CLAUDE.md rule that experimental_models is for non-animal systems.

🐁

Animal Models

5

Thra1PV/+ dominant-negative TR-alpha1 mouse

A knock-in mouse expressing a frameshift TR-alpha1 mutant that shares its mutated C-terminal sequence with human THRA frameshift variants. Crossing it with the Ncor1-delta-ID mouse, whose NCOR1 cannot be recruited by the mutant receptor, partially reverses growth retardation, delayed bone development and infertility - which makes this the experiment that established corepressor recruitment as the operative mechanism in vivo rather than an in vitro inference.

Species

Mouse

Genotype

Thra1PV/+ (frameshift TRalpha1PV mutant, heterozygous)

Publication

PMID:23610395

Pathograph links

Persistent Corepressor Occupancy at Thyroid Hormone Response Elements recapitulates fidelity: high observes: molecular The defining test: removing the mutant receptor's ability to recruit NCOR1 relieves the phenotype, so the phenotype is a consequence of corepressor recruitment.

Limitations: The rescue arm uses a genetically engineered NCOR1 that cannot be recruited, not a pharmacological intervention, so it establishes mechanism without demonstrating a tractable human target. The rescue is also explicitly partial.

Show evidence (1 reference)

PMID:23610395 SUPPORT Model Organism

"Thus, the aberrant recruitment of NCOR1 by TRα1 mutants could lead to clinical hypothyroidism in humans."

The authors' own conclusion that aberrant NCOR1 recruitment is the mechanism, which is the claim this link attests.

Impaired Skeletal Maturation partially recapitulates fidelity: moderate observes: organism Reproduces growth retardation and delayed bone development, both partially reversible by blocking NCOR1 recruitment.

Limitations: The mouse additionally shows infertility, which is not a reported feature of human RTH-alpha, so the phenotype is not a clean match; and the human skeletal picture includes epiphyseal dysgenesis and delayed dentition that the cited work does not assess.

Show evidence (1 reference)

PMID:23610395 SUPPORT Model Organism

"The severe retarded growth, infertility, and delayed bone development were partially reverted in Thra1(PV/+) mice expressing NCOR1ΔID."

Names the skeletal and growth phenotypes and their partial reversal, supporting PARTIALLY_RECAPITULATES rather than RECAPITULATES.

Impaired Terminal Erythroid Differentiation recapitulates fidelity: high observes: cellular TR-alpha1PV directly suppresses key erythroid genes and impairs erythroid progenitor differentiation and terminal erythropoiesis; blocking NCOR1 recruitment corrects both. The corresponding human feature - anaemia in about 77% of reported cases - is one of the commonest findings.

Limitations: The mouse rescue corrects erythroid differentiation, whereas human anaemia largely persists on levothyroxine. That is not a contradiction - the interventions differ - but it means the model's reversibility should not be read as predicting treatment response.

Show evidence (1 reference)

PMID:29273766 SUPPORT Model Organism

"Thyroid hormone receptor α (THRA) gene mutations, via dominant negative mode, cause erythroid abnormalities in patients."

Anchors the mouse erythroid work to the human erythroid phenotype, supporting this model as informative for the node.

Show evidence (1 reference)

PMID:23610395 SUPPORT Model Organism

"TRα1PV shares the same C-terminal mutated sequences as those of patients with frameshift mutations of the THRA gene."

Establishes this model's construct validity for human RTH-alpha: the mouse allele carries the same mutated C-terminal sequence as human THRA frameshift variants, rather than an arbitrary disruption of the gene.

THRA-PV skeletal muscle model

The same dominant-negative frameshift allele studied for skeletal muscle. Myoblasts show reduced proliferation and myogenic differentiation, muscle regeneration after cardiotoxin injury is impaired, and muscle mass is lost with age. The mechanism identified is persistent COUP-TFII (Nr2f2) expression, which interacts with TR-alpha and modulates its binding to thyroid hormone response elements; silencing COUP-TFII restores myogenic potential.

Species

Mouse

Genotype

THRA-PV (frameshift THRA mutant)

Publication

PMID:33633251

Pathograph links

Impaired Skeletal Muscle Maintenance and Regeneration recapitulates fidelity: moderate observes: tissue Reproduces impaired regeneration after injury and age-associated muscle loss, and identifies a specific transcriptional intermediary.

Limitations: The human counterpart of this node is a mildly raised creatine kinase, not a documented regeneration failure or age-related sarcopenia, so the model is considerably more informative about the mechanism than about the human phenotype. Cardiotoxin-induced injury is also not a physiological human exposure.

Show evidence (1 reference)

PMID:33633251 SUPPORT Model Organism

"Silencing of COUP-TFII expression restores in vitro myogenic potential of THRA-PV myoblasts and shifts the mRNA expression profile closer to WT myoblasts."

The rescue experiment identifying COUP-TFII as the intermediary, which is what makes this model informative for the muscle node rather than merely descriptive of it.

Show evidence (1 reference)

PMID:33633251 SUPPORT Model Organism

"Myoblasts derived from THRA-PV mice show reduced proliferation and myogenic differentiation in in vitro models"

Supports treating this model as informative for skeletal muscle: the cellular defect is demonstrable in myoblasts derived from the mutant animals, not only at whole-muscle level.

TR-alpha1 mutant cardiac telemetry mouse

Cardiac telemetry in male TR-alpha1 mutant mice localized the bradycardia of RTH-alpha to the heart itself rather than to autonomic outflow, and transcriptomics showed preserved T3-dependent upregulation of the pacemaker channels Hcn2 and Hcn4 alongside irreversibly reduced expression of other heart-rate ion channel genes. Raising maternal T3 in utero restored that expression and the DNA methylation of Ryr2, implying a developmental window.

Species

Mouse

Genotype

TRalpha1 mutant (male)

Publication

PMID:37286550

Pathograph links

Reduced Intrinsic Cardiac Chronotropic Drive recapitulates fidelity: high observes: tissue Reproduces the persistent bradycardia and demonstrates it is intrinsic to the heart, matching the clinical observation that thyroxine does not raise heart rate in patients.

Limitations: Only male mice were studied. The in utero maternal T3 rescue has no human counterpart - RTH-alpha is not diagnosed prenatally, precisely because there is no screening signal - so the developmental-window finding is not currently actionable.

Show evidence (1 reference)

PMID:37286550 SUPPORT Model Organism

"Transcriptomic analyses show preserved, thyroid hormone (T3)-dependent upregulation of pacemaker channels (Hcn2, Hcn4), but irreversibly reduced expression of several ion channel genes controlling heart rate."

Identifies which cardiac target genes are and are not still T3-responsive, which is the mechanistic content of this link.

Show evidence (1 reference)

PMID:37286550 SUPPORT Model Organism

"Mutations in thyroid hormone receptor α1 (TRα1) cause Resistance to Thyroid Hormone α (RTHα), a disorder characterized by hypothyroidism in TRα1-expressing tissues including the heart."

Frames the heart as one of the TR-alpha1-dependent tissues affected in RTH-alpha, which is what makes a TR-alpha1 mutant mouse the right system for the cardiac node.

thraa / thrab CRISPR dominant-negative zebrafish

Germline-transmissible CRISPR/Cas9 dominant-negative alleles in the two duplicated zebrafish thra genes. Homozygous thrab mutants show severe growth retardation with markedly suppressed growth hormone and IGF1 expression, while homozygous thraa mutants are only mildly affected. The same species is the model in which the corepressor-dissociating ligand analogue ES08 rescued developmental anomalies.

Species

Zebrafish

Genotype

thrab 1-bp insertion and thraa 8-bp insertion dominant-negative alleles

Publication

PMID:31952464

Pathograph links

Impaired Skeletal Maturation partially recapitulates fidelity: low observes: organism Reproduces severe postlarval growth retardation and identifies suppressed gh1 and igf1 expression as a proximate cause.

Limitations: Zebrafish have two thra paralogues where humans have one, and the phenotype partitions unequally between them, so the genotype is not comparable to a human heterozygote. The informative alleles are homozygous, whereas human RTH-alpha is heterozygous and dominant-negative. Zebrafish also have no growth plate, so endochondral ossification - the mechanism this node names - is not what is being observed.

Divergences from the human mechanism

species mismatch qualifying

The thra locus is duplicated in zebrafish into thraa and thrab, and the growth phenotype is carried almost entirely by thrab. There is no single ortholog whose disruption corresponds to a human THRA heterozygote, so allele dosage and gene identity both diverge.

proxy quantity qualifying

The measured quantity is body growth with gh1 and igf1 transcript levels. The node's quantity is growth plate chondrocyte maturation and endochondral ossification, which zebrafish do not have.

Show evidence (1 reference)

PMID:31952464 SUPPORT Model Organism

"Expression of the growth hormone (gh1) and insulin-like growth factor 1 was markedly suppressed in homozygous thrab 1-bp ins (m/m) mutants."

Gives the molecular correlate of the growth phenotype in this model, which is what the link is citing it for.

Show evidence (1 reference)

PMID:31952464 SUPPORT Model Organism

"Using CRISPR/Cas9-mediated targeted mutagenesis, we created dominant negative mutations in the two duplicated thra genes."

Records how the model was made, including that the engineered alleles are dominant-negative rather than null - the property that matters for comparability with human RTH-alpha - and that there are two paralogues, which is the property that limits it.

Low-T3-affinity TR-alpha1 knock-in mouse (TH rescue model)

A heterozygous knock-in mouse whose TR-alpha1 binds thyroid hormone with 10-fold lower affinity, producing extreme anxiety, reduced recognition memory and locomotor dysfunction. Its value here is the rescue design rather than the phenotype: it separates the CNS consequences into two classes with different therapeutic windows. Anxiety and memory deficits were relieved by high-dose thyroid hormone given in adulthood, correlating with normalized GABAergic inhibitory interneurons in hippocampal CA1, whereas the locomotor dysfunction required post-natal treatment and was linked to otherwise delayed cerebellar development.

Species

Mouse

Genotype

TRalpha1 knock-in with 10-fold reduced thyroid hormone affinity, heterozygous

Publication

PMID:16131613

Pathograph links

Impaired Central Nervous System Thyroid Hormone Action rescues fidelity: moderate observes: organism Thyroid hormone rescues part of the CNS phenotype, and the part it rescues depends on when it is given. This is the closest experimental evidence bearing on whether levothyroxine started late can help, which is the open clinical question for this disorder.

Limitations: The lesion is reduced ligand affinity, not the dominant-negative corepressor retention that causes human RTH-alpha, so a hormone-dose rescue is expected to work better here than in a patient whose mutant receptor is transcriptionally inert. The rescued readouts are rodent behavioural assays (anxiety, recognition memory, locomotion), which map only loosely onto the human phenotype of dyspraxia, dysarthria and reduced IQ. Treatment was high-dose thyroid hormone in a mouse, not a clinical levothyroxine regimen.

Divergences from the human mechanism

proxy quantity qualifying

The measured quantities are murine anxiety, recognition memory and locomotor performance. The node's quantity is impaired thyroid hormone action in the human central nervous system, manifesting as developmental delay, dyspraxia and intellectual disability.

Show evidence (2 references)

PMID:16131613 SUPPORT Model Organism

"The anxiety and memory deficiencies were relieved by treatment with high levels of TH in adulthood, an effect that correlated with a normalization of GABAergic inhibitory interneurons in the hippocampal CA1 region."

The adult-rescuable arm, with its cellular correlate in GABAergic interneurons - the same cell population the human epilepsy association is attributed to.

+ 1 more reference

Show evidence (1 reference)

PMID:16131613 SUPPORT Model Organism

"we introduced a mutation into the mouse TRalpha1 gene that lowers affinity to thyroid hormone (TH) 10-fold"

States the construct, which is what bounds this model's relevance: reduced ligand affinity rather than the dominant-negative mechanism of human RTH-alpha.

{ }

Source YAML

click to show

name: Resistance to Thyroid Hormone Alpha
creation_date: "2026-09-10T00:00:00Z"
category: Mendelian
synonyms:
- RTH-alpha
- RTHa
- resistance to thyroid hormone due to a mutation in thyroid hormone receptor alpha
- congenital nongoitrous hypothyroidism 6
- CHNG6
- THRA-related resistance to thyroid hormone
description: >-
  Resistance to thyroid hormone alpha (RTH-alpha) is an autosomal dominant
  disorder of thyroid hormone action caused by heterozygous, dominant-negative
  variants in THRA, which encodes thyroid hormone receptor alpha. The mutant
  TR-alpha retains DNA binding and heterodimerization with the retinoid X
  receptor at thyroid hormone response elements, and several mutants still bind
  T3, but they have lost ligand-dependent transactivation and fail to release
  the NCoR/SMRT corepressor complex. The lesion is therefore not a simple
  halving of receptor dose: the mutant receptor actively silences T3 target
  genes and inhibits the co-expressed wild-type allele, which is why a
  heterozygous variant produces disease.

  Because TR-alpha and TR-beta have different tissue distributions, the
  consequence is a dissociation rather than a uniform hypothyroidism. Tissues
  that signal predominantly through TR-alpha - bone, gastrointestinal tract,
  heart, central nervous system, skeletal muscle and the erythroid lineage -
  behave as hypothyroid, while the hypothalamic-pituitary-thyroid axis runs on
  TR-beta and remains responsive. TSH is therefore normal or only mildly
  raised, free T4 is low or low-normal, free T3 is high-normal or frankly high,
  the T4/T3 ratio is subnormal and reverse T3 is low. This near-normal thyroid
  function profile is the whole clinical problem: conventional TSH-based
  newborn screening for congenital hypothyroidism is built on an elevated TSH
  and so does not identify these children, and the diagnosis is typically made
  years later, or in adulthood, or not at all.

  RTH-alpha is first a pediatric entity. The presenting picture is growth
  retardation with delayed bone age and epiphyseal dysgenesis, macrocephaly and
  a coarse flat facies, delayed dentition and delayed fontanelle closure,
  severe constipation, normocytic or macrocytic anaemia, raised creatine
  kinase, bradycardia in a minority, and delayed motor and speech milestones
  with variable intellectual disability. Levothyroxine is the only treatment in
  use and is partial and tissue-selective by the same logic that causes the
  disease: it relieves constipation and lowers creatine kinase, improves growth
  and development in some children, and leaves other features - anaemia in
  particular - unchanged.
disease_term:
  preferred_term: resistance to thyroid hormone alpha
  term:
    id: MONDO:0013757
    label: congenital nongoitrous hypothyroidism 6
parents:
- thyroid hormone resistance syndrome
- impaired sensitivity to thyroid hormone
mappings:
  mondo_mappings:
  - term:
      id: MONDO:0013757
      label: congenital nongoitrous hypothyroidism 6
    mapping_predicate: skos:exactMatch
    notes: >-
      The anchoring term. MONDO defines it as "Any hypothyroidism, congenital,
      nongoitrous in which the cause of the disease is a mutation in the THRA
      gene" and cross-references OMIM:614450, DOID:0070128, GARD:0024946,
      MEDGEN:482447 and UMLS:C3280817.
  - term:
      id: MONDO:0034216
      label: resistance to thyroid hormone due to a mutation in thyroid hormone
        receptor alpha
    mapping_predicate: skos:exactMatch
    notes: >-
      Asserted as an exact match, not a narrower or related one, because the two
      MONDO terms are an unmerged duplicate pair denoting the same THRA disease.
      MONDO:0034216 carries no logical definition and cross-references
      Orphanet:566231, GARD:0022275, MEDGEN:1830097 and UMLS:C5680127;
      MONDO:0013757 cross-references OMIM:614450. Orphanet's own ORDO record for
      566231 ("Resistance to thyroid hormone due to a mutation in thyroid
      hormone receptor alpha", synonyms RTHa and "Resistance to thyroid hormone
      alpha") cross-references BOTH MONDO:0034216 and OMIM:614450, so the two
      MONDO identifiers trace to the same source concept through different
      vocabularies. Neither term asserts a has-exact-match to the other and
      neither is an ancestor of the other - MONDO:0013757 sits under
      MONDO:0000045 (hypothyroidism, congenital, nongoitrous) and MONDO:0019995
      (peripheral resistance to thyroid hormones), while MONDO:0034216 sits
      under MONDO:0001328 (thyroid hormone resistance syndrome) - so this is a
      MONDO integration gap rather than a real split, and both should be
      retired from the curation queue by this entry. Checked against OLS
      (ols:mondo and ols:ordo) on 2026-09-10; the prior reasoning recorded in
      Generalized_Resistance_to_Thyroid_Hormone, which named MONDO:0034216 as
      the RTH-alpha term, is consistent with this and simply predates the
      CHNG6-keyed stub.
classifications:
  harrisons_chapter:
  - classification_value: ENDOCRINOLOGY_METABOLISM
    notes: >-
      A monogenic disorder of thyroid hormone action with a characteristic
      discordant thyroid function profile, placing it in endocrinology and
      metabolism.
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
    notes: >-
      A single-gene disorder whose diagnosis rests on THRA sequencing, because
      the biochemical phenotype is near-normal. The presenting picture is
      pediatric - growth retardation, delayed bone age, delayed milestones,
      constipation and anaemia in infancy and childhood - and the therapeutic
      window for levothyroxine appears to be early childhood, but
      HarrisonsChapterEnum has no PEDIATRICS value to record that.
prevalence:
- population: Worldwide, published cases
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    As of the 2021 review of all published cases, 40 affected individuals from
    28 families carrying 25 distinct THRA variants had been reported. Counted
    cases rather than an estimated population prevalence, because no
    population-based ascertainment exists and the biochemical profile is
    near-normal, so the published count is a floor rather than an estimate.
    Orphanet's own epidemiology entry for ORPHA:566231 records a worldwide
    point prevalence of <1/1,000,000 and 35 reported cases, but the Orphanet
    bulk XML is not present in this checkout, so no ORPHA snippet is cited
    here.
  evidence:
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "To date, 40 cases (13 adults, 27 children) from 28 different families with 25 different variants inTHRAgene have been published"
    explanation: >-
      Gives the published case count, family count and variant count behind the
      ULTRA_RARE class. The missing spaces in "inTHRAgene" are an artifact of
      the cached full text and are reproduced verbatim rather than corrected.
progression:
- phase: Infancy and early childhood
  notes: >-
    Presentation is in the first years of life, and almost always for something
    other than thyroid disease: growth faltering, delayed motor and speech
    milestones, or severe constipation. Delayed bone age, epiphyseal dysgenesis,
    wormian bones, delayed dentition and late fontanelle closure are
    childhood-specific skeletal findings. Newborn screening has already missed the
    diagnosis by this point, because it is TSH-based.
  evidence:
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In infants with RTHα, delayed milestones for motor and speech abilities are the most common symptoms, noted in 34 among 40 cases (85%)"
    explanation: Establishes what brings these children to attention, and when.
- phase: Adulthood
  notes: >-
    The phenotype attenuates rather than progresses, which is itself a diagnostic
    hazard: epiphyseal dysgenesis present in childhood is absent on adult imaging,
    and the biochemical abnormalities become subtler, so an adult relative of an
    index case can look near-normal on thyroid function tests. What persists is
    anaemia, constipation, and the cognitive and motor phenotype; hepatic steatosis
    and raised LDL/HDL are reported in adults. Untreated adults show a more
    pronounced phenotype than patients treated from childhood.
  evidence:
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the individual clinical picture or laboratory findings becoming less remarkable with age"
    explanation: >-
      States the attenuation directly. This is why the entry treats adult
      ascertainment as harder than paediatric, not easier.
  - reference: PMID:42301959
    reference_title: "Intrafamilial and Age-Dependent Variability in Resistance to Thyroid Hormone Alpha: A Case Report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This report adds novel insight by documenting intrafamilial variability and age-related attenuation of biochemical abnormalities in a family carrying a previously described THRA variant."
    explanation: >-
      Independent documentation of age-related attenuation, in a kindred where the
      mother carried the same variant as her affected daughters.
inheritance:
- name: Autosomal dominant
  inheritance_term:
    preferred_term: autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  description: >-
    Heterozygous THRA variants are sufficient to cause disease because the
    mutant receptor acts dominant-negatively on the wild-type allele rather
    than merely reducing receptor dose. Both de novo occurrence and
    parent-to-child transmission are documented; the index cases of 2012 and
    several later reports were de novo, while a four-member first-degree
    related kindred sharing p.Ala263Val has been described.
  evidence:
  - reference: PMID:37469961
    reference_title: Clinical and Biochemical Characteristics of Untreated Adult Patients With Resistance to Thyroid Hormone Alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Heterozygous pathogenic variants in THRA are associated with resistance to thyroid hormone alpha (RTHα), causing autosomal dominant nongoitrous congenital hypothyroidism."
    explanation: >-
      States the heterozygous, autosomal dominant mode directly, and is also
      the clearest published statement that the RTH-alpha phenotype and the
      "autosomal dominant nongoitrous congenital hypothyroidism" (CHNG6)
      concept are one disease - the basis for the mondo_mappings decision above.
  - reference: PMID:22168587
    reference_title: A mutation in the thyroid hormone receptor alpha gene.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a de novo heterozygous nonsense mutation in a gene encoding thyroid hormone receptor alpha (THRA) and generating a mutant protein that inhibits wild-type receptor action in a dominant negative manner"
    explanation: >-
      The index case: a de novo heterozygous variant acting dominant-negatively,
      which is why one altered allele suffices.
genetic:
- name: THRA
  gene_term:
    preferred_term: THRA
    term:
      id: hgnc:11796
      label: THRA
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  notes: >-
    THRA encodes thyroid hormone receptor alpha. Disease-causing variants are
    heterozygous and cluster in the C-terminal ligand-binding domain; nonsense,
    frameshift and missense variants near the C-terminus produce a more severe
    phenotype than missense variants in the more N-terminal segment shared by
    the TR-alpha1 and TR-alpha2 isoforms. No phenotype has been attributed to
    the TR-alpha2 consequences of these variants.
  evidence:
  - reference: PMID:37469961
    reference_title: Clinical and Biochemical Characteristics of Untreated Adult Patients With Resistance to Thyroid Hormone Alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The pathogenic THRA variants described so far are most frequently located in the C-terminal ligand-binding domain (LBD)"
    explanation: Locates the disease-causing variants in the ligand-binding domain.
  - reference: PMID:25670821
    reference_title: Thyroid hormone resistance syndrome due to mutations in the thyroid hormone receptor α gene (THRA).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We observed a genotype-phenotype correlation, with milder outcomes for missense mutations and more severe phenotypical effects for truncating mutations."
    explanation: >-
      Establishes the variant-class to severity correlation in a six-patient,
      five-family cohort followed for 18 years.
  - reference: PMID:28471274
    reference_title: Contrasting Phenotypes in Resistance to Thyroid Hormone Alpha Correlate with Divergent Properties of Thyroid Hormone Receptor α1 Mutant Proteins.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neither A263V nor L274P mutations exhibited gain or loss of function in the TRα2 background, and no additional phenotype attributable to this was discerned."
    explanation: >-
      Supports confining the mechanistic claim to TR-alpha1 despite THRA
      encoding both isoforms.
pathophysiology:
- name: THRA Dominant-Negative Receptor Variant
  biological_scale: MOLECULAR
  role: trigger
  description: >-
    A heterozygous THRA variant, usually in the C-terminal ligand-binding
    domain, produces a TR-alpha1 protein that has lost ligand-dependent
    transcriptional activation. Critically, the mutant is not simply inert: it
    retains DNA binding and retinoid X receptor heterodimerization, and crystal
    structures show that several mutants devoid of transactivation function
    still bind T3. The defect is therefore downstream of ligand occupancy, in
    the conformational change that should convert the receptor from a repressor
    into an activator.
  mechanism_confidence: ESTABLISHED
  genes:
  - preferred_term: THRA
    term:
      id: hgnc:11796
      label: THRA
  molecular_functions:
  - preferred_term: TR-alpha1 ligand-dependent nuclear receptor activity
    modifier: LOSS_OF_FUNCTION
    term:
      id: GO:0004879
      label: nuclear receptor activity
  genetic_context:
    gene:
      preferred_term: THRA
      term:
        id: hgnc:11796
        label: THRA
    variant_origin: GERMLINE
    zygosity: HETEROZYGOUS
    functional_impact_category: DOMINANT_NEGATIVE
    description: >-
      The functional impact is recorded as DOMINANT_NEGATIVE rather than
      LOSS_OF_FUNCTION or PARTIAL_LOSS_OF_FUNCTION because the mutant receptor
      inhibits the function of the co-expressed wild-type receptor, which is
      what makes a heterozygous variant pathogenic and makes the phenotype more
      severe than THRA haploinsufficiency would be.
  downstream:
  - target: Persistent Corepressor Occupancy at Thyroid Hormone Response Elements
    causal_link_type: DIRECT
    description: >-
      Because the mutant cannot undergo the T3-induced conformational change
      that dissociates corepressor, the receptor-corepressor complex remains
      assembled on target gene promoters.
    evidence:
    - reference: PMID:34871063
      reference_title: Structure-Guided Approach to Relieving Transcriptional Repression in Resistance to Thyroid Hormone α.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "RTHα-associated TRα mutants devoid of ligand-dependent transcription activation function unexpectedly retain the ability to bind thyroid hormone."
      explanation: >-
        Supports this specific step: ligand still binds, so the failure is in
        the coupling between ligand binding and corepressor release rather than
        in hormone access to the receptor.
  - target: Sparing of TR-beta-Dependent Tissues and the Pituitary Thyrotroph
    causal_link_type: DIRECT
    description: >-
      The lesion is confined to THRA, so TR-beta1 and TR-beta2 are structurally
      and functionally intact and the tissues that depend on them continue to
      respond to thyroid hormone normally.
  evidence:
  - reference: PMID:22168587
    reference_title: A mutation in the thyroid hormone receptor alpha gene.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a de novo heterozygous nonsense mutation in a gene encoding thyroid hormone receptor alpha (THRA) and generating a mutant protein that inhibits wild-type receptor action in a dominant negative manner"
    explanation: >-
      The founding observation that the THRA mutant protein inhibits wild-type
      receptor action, i.e. acts dominant-negatively.
  - reference: PMID:26303090
    reference_title: Resistance to thyroid hormone due to defective thyroid receptor alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "TR binds preferentially to regulatory DNA sequences (thyroid hormone response elements, TREs) in target gene promoters as a heterodimer with the retinoid X receptor (RXR)"
    explanation: >-
      Establishes that the receptor occupies thyroid hormone response elements
      as an RXR heterodimer, which is the structural basis for a non-functional
      mutant being able to occupy and silence a promoter rather than simply
      vacating it.
- name: Persistent Corepressor Occupancy at Thyroid Hormone Response Elements
  biological_scale: MOLECULAR
  description: >-
    In the unliganded state a thyroid hormone receptor recruits a corepressor
    complex containing NCoR or SMRT together with histone deacetylase, which
    represses target gene transcription; T3 binding normally dissociates this
    complex and allows coactivator recruitment. The RTH-alpha mutant receptor
    fails to make that switch, so the repressive complex stays bound. This is
    the step that distinguishes RTH-alpha from a loss of receptor: the promoter
    is not merely unactivated, it is actively silenced, and the wild-type
    receptor on the same response element is held hostage.
  mechanism_confidence: ESTABLISHED
  molecular_functions:
  - preferred_term: persistent NCoR/SMRT corepressor binding by mutant TR-alpha1
    modifier: INCREASED
    term:
      id: GO:0001222
      label: transcription corepressor binding
  biological_processes:
  - preferred_term: repression of T3-responsive target gene transcription
    modifier: INCREASED
    term:
      id: GO:0000122
      label: negative regulation of transcription by RNA polymerase II
  downstream:
  - target: Transcriptional Silencing of T3 Target Genes in TR-alpha-Expressing Tissues
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:34871063
      reference_title: Structure-Guided Approach to Relieving Transcriptional Repression in Resistance to Thyroid Hormone α.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "This disorder is characterized by tissue-specific hormone refractoriness and hypothyroidism due to the inhibition of target gene expression by mutant TRα-corepressor complexes."
      explanation: >-
        States the causal step directly - the mutant receptor-corepressor
        complex is what inhibits target gene expression.
  evidence:
  - reference: PMID:34871063
    reference_title: Structure-Guided Approach to Relieving Transcriptional Repression in Resistance to Thyroid Hormone α.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Receptor occupancy by a ligand (T3) promotes the dissociation of this corepressor complex with the relief of transcriptional repression"
    explanation: >-
      States the normal ligand-triggered corepressor dissociation step. It is
      precisely this step that the RTH-alpha mutant fails to execute, which is
      what leaves the repressive complex in place on the response element.
  - reference: PMID:37469961
    reference_title: Clinical and Biochemical Characteristics of Untreated Adult Patients With Resistance to Thyroid Hormone Alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A key molecular pathogenic defect may be persistent co-repressor binding, rather than coactivator recruitment per se."
    explanation: >-
      Attributes the pathogenic defect to persistent corepressor binding
      specifically, as opposed to a failure of coactivator recruitment.
  - reference: PMID:23837191
    reference_title: "RTHα, a newly recognized phenotype of the resistance to thyroid hormone (RTH) syndrome in patients with THRA gene mutations."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "When T3binds to TRs on positively regulated genes, corepressor proteins are released and replaced by coactivators leading to increased gene transcription."
    explanation: >-
      States the normal corepressor-to-coactivator exchange that the mutant
      receptor fails to perform. The missing space in "T3binds" is an artifact
      of the cached full text and is quoted as it appears.
- name: Transcriptional Silencing of T3 Target Genes in TR-alpha-Expressing Tissues
  biological_scale: CELLULAR
  description: >-
    In every cell whose thyroid hormone response is carried mainly by
    TR-alpha1, T3-responsive genes are held repressed despite normal
    intracellular hormone. The resulting state is a cell-autonomous
    hypothyroidism that is refractory to circulating hormone, which is why the
    phenotype is tissue-patterned rather than generalized.
  mechanism_confidence: ESTABLISHED
  biological_processes:
  - preferred_term: TR-alpha1-mediated thyroid hormone receptor signaling
    modifier: LOSS_OF_FUNCTION
    term:
      id: GO:0002154
      label: thyroid hormone receptor signaling pathway
  notes: >-
    modifier is LOSS_OF_FUNCTION rather than DECREASED deliberately. The claim
    is qualitative, not quantitative: the pathway is not running below its
    normal level in response to a normal signal, it has been taken outside
    ligand control, so increasing the hormone concentration does not simply
    scale the response back up. That is also why levothyroxine is only
    partially effective.
  downstream:
  - target: Impaired Skeletal Maturation
    causal_link_type: DIRECT
  - target: Impaired Gastrointestinal Motility
    causal_link_type: DIRECT
  - target: Impaired Terminal Erythroid Differentiation
    causal_link_type: DIRECT
  - target: Reduced Intrinsic Cardiac Chronotropic Drive
    causal_link_type: DIRECT
  - target: Impaired Skeletal Muscle Maintenance and Regeneration
    causal_link_type: DIRECT
  - target: Impaired Central Nervous System Thyroid Hormone Action
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:23837191
    reference_title: "RTHα, a newly recognized phenotype of the resistance to thyroid hormone (RTH) syndrome in patients with THRA gene mutations."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "TRβ predominates in the hypothalamic-pituitary-thyroid axis, liver, and kidney, whereas TRα transduces much of the thyroid hormone signaling in the heart, skeletal muscle, central nervous system, bone, and intestines"
    explanation: >-
      Names the tissues whose thyroid hormone signaling runs through TR-alpha,
      which is the set of tissues this node applies to and the reason the
      downstream consequences are the ones listed.
  - reference: PMID:34871063
    reference_title: Structure-Guided Approach to Relieving Transcriptional Repression in Resistance to Thyroid Hormone α.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "ES08, which dissociates corepressor from mutant human TRα more efficaciously than T3. ES08 rescues developmental anomalies in a zebrafish model of RTHα"
    explanation: >-
      A pharmacological test of this node: a ligand analogue selected for its
      ability to dissociate corepressor from the mutant receptor relieves the
      phenotype, which supports target gene silencing as the operative lesion
      rather than an unrelated consequence of the variant.
- name: Sparing of TR-beta-Dependent Tissues and the Pituitary Thyrotroph
  biological_scale: ORGANISM
  description: >-
    TR-beta2 carries the thyroid hormone feedback signal in the hypothalamus
    and pituitary thyrotroph, and TR-beta1 predominates in liver and kidney.
    None of these is affected by a THRA variant, so the negative feedback loop
    continues to sense circulating hormone normally and sets TSH at a
    near-normal level. The intact axis is not a benign detail: it is what
    removes the laboratory signal that would otherwise announce the disease.
  mechanism_confidence: ESTABLISHED
  biological_processes:
  - preferred_term: TR-beta-mediated thyroid hormone receptor signaling in the HPT axis
    term:
      id: GO:0002154
      label: thyroid hormone receptor signaling pathway
  downstream:
  - target: Discordant Thyroid Function Profile with Non-Elevated TSH
    causal_link_type: DIRECT
    description: >-
      With pituitary feedback intact and peripheral TR-alpha tissues
      unresponsive, the serum profile settles into the characteristic
      dissociation rather than the raised TSH of primary hypothyroidism.
    evidence:
    - reference: PMID:28527577
      reference_title: Resistance to Thyroid Hormone due to Heterozygous Mutations in Thyroid Hormone Receptor Alpha.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "RTHα should be suspected in subjects with even mild clinical features of hypothyroidism together with high/high-normal (F)T3, low/low-normal (F)T4, and normal TSH."
      explanation: >-
        States the resulting profile - hypothyroid features with a normal TSH -
        which is the consequence this edge asserts.
  evidence:
  - reference: PMID:23837191
    reference_title: "RTHα, a newly recognized phenotype of the resistance to thyroid hormone (RTH) syndrome in patients with THRA gene mutations."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "TRβ predominates in the hypothalamic-pituitary-thyroid axis, liver, and kidney, whereas TRα transduces much of the thyroid hormone signaling in the heart, skeletal muscle, central nervous system, bone, and intestines"
    explanation: >-
      Establishes that the hypothalamic-pituitary-thyroid axis is TR-beta
      territory and therefore unaffected by a THRA variant.
- name: Discordant Thyroid Function Profile with Non-Elevated TSH
  biological_scale: ORGANISM
  description: >-
    The biochemical signature is free T3 in the upper half of the reference
    range or frankly high, free T4 low or in the lower half of the range, a
    subnormal T4/T3 ratio, low reverse T3, and a TSH that is normal or at most
    mildly raised. Each component can individually fall inside its reference
    interval, particularly in adults, so the abnormality is often only visible
    as the ratio.
  mechanism_confidence: ESTABLISHED
  downstream:
  - target: Escape from TSH-Based Newborn Screening and Diagnostic Delay
    causal_link_type: DIRECT
    description: >-
      Newborn screening for congenital hypothyroidism is predicated on an
      elevated TSH. A disorder whose TSH is normal is therefore invisible to it,
      and ascertainment falls back on clinical suspicion years later.
    evidence:
    - reference: PMID:39201272
      reference_title: "Normal Values for the fT3/fT4 Ratio: Centile Charts (0-29 Years) and Their Application for the Differential Diagnosis of Children with Developmental Delay."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Primary congenital hypothyroidism is easily diagnosed on the basis of elevated plasma levels of thyroid-stimulating hormone (TSH). In contrast, in the rare disorders of thyroid hormone resistance, TSH and, in mild cases, also thyroid hormone levels are within the normal range."
      explanation: >-
        Contrasts the TSH-based diagnostic route for congenital hypothyroidism
        with the normal TSH of the resistance disorders, which is exactly the
        causal step from the biochemical profile to failed detection.
  evidence:
  - reference: PMID:25670821
    reference_title: Thyroid hormone resistance syndrome due to mutations in the thyroid hormone receptor α gene (THRA).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the thyroid profile showed low free thyroxine (fT4) levels coupled with high free T3 (fT3), leading to an altered T4 : T3 ratio, along with normal thyroid-stimulating hormone levels"
    explanation: >-
      Reports the full discordant profile, including the normal TSH, in a
      longitudinally characterized multi-family cohort.
  - reference: PMID:26303090
    reference_title: Resistance to thyroid hormone due to defective thyroid receptor alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Biochemical abnormalities include low/low-normal T4 and high/high-normal T3 concentrations, a subnormal T4/T3 ratio, variably reduced reverse T3, raised muscle creatine kinase and mild anaemia."
    explanation: >-
      Adds the subnormal T4/T3 ratio and the reduced reverse T3 to the profile,
      and links them to the raised creatine kinase and anaemia.
- name: Escape from TSH-Based Newborn Screening and Diagnostic Delay
  biological_scale: ORGANISM
  description: >-
    The practical consequence of an intact TR-beta feedback axis is that the
    disorder is not captured by population newborn screening and is commonly
    diagnosed only when a child is investigated for developmental delay, short
    stature or constipation - or, in adults, incidentally through a gene panel
    run for intellectual disability. Untreated adults show a more pronounced
    phenotype than patients treated from childhood, so the delay is not
    neutral.
  mechanism_confidence: ESTABLISHED
  evidence:
  - reference: PMID:37469961
    reference_title: Clinical and Biochemical Characteristics of Untreated Adult Patients With Resistance to Thyroid Hormone Alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The delay in diagnosis is probably due to normal thyroid function tests."
    explanation: >-
      Attributes the diagnostic delay specifically to the normal thyroid
      function tests, in a series of four adults who reached adulthood
      undiagnosed and untreated.
  - reference: PMID:24847461
    reference_title: Clinical Consequences of Mutations in Thyroid Hormone Receptor-α1.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the first humans carrying a defect in TRα1 were not suspected of having a THRA gene mutation initially"
    explanation: >-
      Records that even the index patients were not suspected of the diagnosis,
      illustrating how little the laboratory profile points to it.
- name: Impaired Skeletal Maturation
  biological_scale: TISSUE
  description: >-
    TR-alpha1 is the receptor through which thyroid hormone drives growth plate
    chondrocyte maturation and ossification. With T3 target genes silenced,
    endochondral ossification and bone age lag, the epiphyses are dysgenetic,
    dentition and fontanelle closure are delayed, and head circumference is
    relatively increased - the cluster reported clinically as skeletal dysplasia
    with macrocephaly.
  mechanism_confidence: ESTABLISHED
  cell_types:
  - preferred_term: growth plate chondrocyte
    term:
      id: CL:1000217
      label: growth plate cartilage chondrocyte
  biological_processes:
  - preferred_term: endochondral ossification at the growth plate
    modifier: DECREASED
    term:
      id: GO:0001958
      label: endochondral ossification
  downstream:
  - target: Short stature
    causal_link_type: DIRECT
  - target: Delayed skeletal maturation
    causal_link_type: DIRECT
  - target: Epiphyseal dysplasia
    causal_link_type: DIRECT
  - target: Macrocephaly
    causal_link_type: DIRECT
  - target: Delayed eruption of teeth
    causal_link_type: DIRECT
  - target: Delayed closure of the anterior fontanelle
    causal_link_type: DIRECT
  - target: Wormian bones
    causal_link_type: DIRECT
  - target: Cranial hyperostosis
    causal_link_type: DIRECT
    description: >-
      Grouped with the other cranial findings as part of the same delayed
      ossification, though the thickened adult calvarium and the childhood wormian
      bones are opposite-looking consequences of it.
  - target: Coarse facial features
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      The round, coarse, flat facies is described in the literature as part of the
      same skeletal dysplasia, but the steps between impaired thyroid-hormone-driven
      skeletal maturation and the specific facial morphology are not characterized,
      hence an indirect link.
  evidence:
  - reference: PMID:26303090
    reference_title: Resistance to thyroid hormone due to defective thyroid receptor alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical features include dysmorphic facies, skeletal dysplasia (macrocephaly, epiphyseal dysgenesis), growth retardation, constipation, dyspraxia and intellectual deficit."
    explanation: >-
      Groups macrocephaly and epiphyseal dysgenesis together as the skeletal
      dysplasia of RTH-alpha, which is why this node carries both as downstream
      consequences rather than splitting them.
  - reference: PMID:23610395
    reference_title: Nuclear receptor corepressor (NCOR1) regulates in vivo actions of a mutated thyroid hormone receptor α.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The severe retarded growth, infertility, and delayed bone development were partially reverted in Thra1(PV/+) mice expressing NCOR1ΔID."
    explanation: >-
      Shows in vivo that the growth and bone phenotype of a dominant-negative
      TR-alpha1 mutant is a consequence of corepressor recruitment, since
      preventing that recruitment partially reverses it.
- name: Impaired Gastrointestinal Motility
  biological_scale: TISSUE
  description: >-
    The intestine is a TR-alpha-dependent tissue and severe constipation was
    part of the presenting picture of the very first reported case. The motility
    defect is measured, not inferred: colonic manometry in RTH-alpha patients
    shows decreased peristalsis. Mouse models carrying the ThraE403X allele show
    extensive intestinal molecular abnormality, confirming that TR-alpha1 acts in
    the gut. What remains unestablished is the cellular locus - enteric neuron
    versus smooth muscle.
  mechanism_confidence: ESTABLISHED
  biological_processes:
  - preferred_term: gastrointestinal smooth muscle contraction
    modifier: DECREASED
    term:
      id: GO:0014831
      label: gastro-intestinal system smooth muscle contraction
  notes: >-
    No cell_types are bound on this node on purpose. Decreased colonic peristalsis
    is documented by manometry, but nothing located names the responsible cell
    type in human RTH-alpha, and binding enteric smooth muscle cell or enteric
    neuron here would assert a localization the cited sources do not make.
    mechanism_confidence was PROVISIONAL in the first draft of this entry, on the
    grounds that reduced motility was inferred from constipation rather than
    measured; it was raised to ESTABLISHED once the colonic manometry finding was
    located. The GO process bound here names smooth muscle contraction, which is
    still a narrower claim than "decreased peristalsis" strictly supports.
  downstream:
  - target: Constipation
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:22168587
    reference_title: A mutation in the thyroid hormone receptor alpha gene.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here we describe a child with classic features of hypothyroidism (growth retardation, developmental retardation, skeletal dysplasia, and severe constipation) but only borderline-abnormal thyroid hormone levels."
    explanation: >-
      Severe constipation in the index case, alongside near-normal hormone
      levels, establishing gut involvement as a core feature rather than an
      incidental one.
  - reference: PMID:35574030
    reference_title: Proteomic Analysis of the Intestinal Resistance to Thyroid Hormone Mouse Model With Thyroid Hormone Receptor Alpha Mutations.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "A total of 1,189 DEPs were identified, including 603 upregulated and 586 downregulated proteins."
    explanation: >-
      Documents extensive intestinal protein dysregulation in the ThraE403X
      mouse, supporting the intestine as a site of TR-alpha1 action. It does not
      by itself demonstrate a motility mechanism - the manometry evidence below
      does that.
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Decreased peristalsis was also observed by colonic manometry in several cases with RTHα"
    explanation: >-
      A measured human finding of reduced colonic motility, which is what moves
      this node from an inference off the constipation phenotype to a
      physiologically observed defect.
- name: Impaired Terminal Erythroid Differentiation
  biological_scale: CELLULAR
  description: >-
    Mutant TR-alpha1 directly represses key erythroid genes, impairing the
    differentiation potential of erythroid progenitors and terminal
    erythropoiesis. In primary erythroid progenitors cultured from RTH-alpha
    patients the defect presents as a shifted balance rather than an outright
    block: cells differentiate, but more slowly, staying larger and more
    c-Kit-positive and becoming glycophorin-A-positive later. Notably the degree of
    abnormality did not track the severity of the underlying TR-alpha defect, and
    induced differentiation and T3 exposure worked normally - so the lesion is in
    spontaneous maturation, not in the capacity to mature. The clinical correlate
    is the normocytic or macrocytic anaemia that is among the most consistent
    findings in RTH-alpha and, unlike constipation, is not reliably corrected by
    levothyroxine.
  mechanism_confidence: ESTABLISHED
  cell_types:
  - preferred_term: erythroid progenitor cell
    term:
      id: CL:0000038
      label: erythroid progenitor cell
  biological_processes:
  - preferred_term: terminal erythroid differentiation
    modifier: DECREASED
    term:
      id: GO:0030218
      label: erythrocyte differentiation
  downstream:
  - target: Anemia
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:29273766
      reference_title: NCOR1 modulates erythroid disorders caused by mutations of thyroid hormone receptor α1.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "we showed that TRα1PV acted directly to suppress the expression of key erythroid genes, causing erythroid defects"
      explanation: >-
        Asserts the causal step from mutant-receptor gene repression to the
        erythroid defect.
  evidence:
  - reference: PMID:29273766
    reference_title: NCOR1 modulates erythroid disorders caused by mutations of thyroid hormone receptor α1.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The expression of NCOR1ΔID ameliorated abnormalities in the peripheral blood indices, and corrected the defective differentiation potential of progenitors in the erythroid lineage."
    explanation: >-
      Places the erythroid defect downstream of corepressor recruitment by the
      mutant receptor: blocking NCOR1 interaction corrects progenitor
      differentiation.
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In humans, 23 among 30 cases with available data (77%) had anemia, and it has been one of the most common findings in humans with RTHα"
    explanation: >-
      Quantifies the human anaemia frequency across the published case series,
      confirming that the mouse erythroid finding corresponds to a common human
      feature.
  - reference: PMID:28911146
    reference_title: "Anemia in Patients With Resistance to Thyroid Hormone α: A Role for Thyroid Hormone Receptor α in Human Erythropoiesis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Inactivating mutations in human TRα affect the balance between proliferation and differentiation of progenitor cells during erythropoiesis, which may contribute to the mild anemia seen in most RTHα patients."
    explanation: >-
      Human evidence for this node, from primary erythroid progenitors of 11
      RTH-alpha patients. This matters beyond adding a citation: without it the
      node rested on mouse data alone, and CLAUDE.md requires that model-organism
      evidence not be the only support for a human phenotype.
  - reference: PMID:28911146
    reference_title: "Anemia in Patients With Resistance to Thyroid Hormone α: A Role for Thyroid Hormone Receptor α in Human Erythropoiesis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "During spontaneous differentiation, RTHα-derived HEPs were larger, more positive for c-Kit (a proliferation marker), and less positive for glycophorin A (a differentiation marker)."
    explanation: >-
      The specific measurement behind the claim - patient-derived progenitors held
      in a more proliferative, less differentiated state.
- name: Reduced Intrinsic Cardiac Chronotropic Drive
  biological_scale: TISSUE
  description: >-
    TR-alpha1 is the predominant receptor isoform in the heart and mediates
    thyroid hormone's chronotropic effect. In RTH-alpha the resulting
    bradycardia is intrinsic to the heart rather than autonomically mediated,
    and in TR-alpha1 mutant mice the pacemaker channels Hcn2 and Hcn4 remain
    T3-responsive while several other heart-rate ion channel genes are
    irreversibly down-regulated. This is why thyroxine does not raise heart rate
    in these patients - a therapeutically important dissociation rather than a
    curiosity.
  mechanism_confidence: ESTABLISHED
  cell_types:
  - preferred_term: cardiac muscle cell
    term:
      id: CL:0000746
      label: cardiac muscle cell
  biological_processes:
  - preferred_term: thyroid hormone-dependent regulation of heart rate
    modifier: DECREASED
    term:
      id: GO:0002027
      label: regulation of heart rate
  downstream:
  - target: Bradycardia
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:37286550
      reference_title: Resistance to thyroid hormone induced tachycardia in RTHα syndrome.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Cardiac telemetry in male, TRα1 mutant, mice indicates that such persistent bradycardia is caused by an intrinsic cardiac defect and not due to altered autonomic control."
      explanation: >-
        Localizes the bradycardia to the heart itself rather than to autonomic
        outflow, which is the causal claim of this edge.
  evidence:
  - reference: PMID:37286550
    reference_title: Resistance to thyroid hormone induced tachycardia in RTHα syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In the heart, TRα1 is the predominant isoform and mediates the known effects of the hormone such as increasing contractility, oxygen consumption, cardiac output as well as heart rate"
    explanation: >-
      Establishes TR-alpha1 as the cardiac isoform carrying the chronotropic
      signal, so its dominant-negative inhibition predicts a rate defect.
- name: Impaired Skeletal Muscle Maintenance and Regeneration
  biological_scale: TISSUE
  description: >-
    TR-alpha is the predominant thyroid hormone receptor isoform in skeletal
    muscle, where it is required for regeneration after injury and for
    maintaining muscle mass. In the THRA-PV mouse, persistent COUP-TFII
    expression in myoblasts blocks myogenic differentiation, and silencing
    COUP-TFII restores it. The corresponding human observation is a raised
    creatine kinase, which falls on levothyroxine treatment.
  mechanism_confidence: ESTABLISHED
  cell_types:
  - preferred_term: skeletal muscle satellite cell
    term:
      id: CL:0000594
      label: skeletal muscle satellite cell
  biological_processes:
  - preferred_term: skeletal muscle regeneration after injury
    modifier: DECREASED
    term:
      id: GO:0043403
      label: skeletal muscle tissue regeneration
  downstream:
  - target: Elevated circulating creatine kinase concentration
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Recorded as indirect with unknown intermediates because no located source
      traces the raised creatine kinase in human RTH-alpha to the specific
      myogenic defect characterized in the mouse; the two are concordant
      observations about the same tissue rather than a demonstrated causal
      chain.
  evidence:
  - reference: PMID:33633251
    reference_title: Persistent COUP-TFII expression underlies the myopathy and impaired muscle regeneration observed in resistance to thyroid hormone-alpha.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "A mouse model of resistance to thyroid hormone carrying a frame-shift mutation in the THRA gene (THRA-PV) is associated with accelerated skeletal muscle loss with aging and impaired regeneration after injury."
    explanation: >-
      Establishes the muscle phenotype in a dominant-negative THRA mouse:
      accelerated muscle loss and impaired regeneration.
  - reference: PMID:33633251
    reference_title: Persistent COUP-TFII expression underlies the myopathy and impaired muscle regeneration observed in resistance to thyroid hormone-alpha.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "THRA is the predominant isoform in skeletal muscle and plays an essential role in skeletal muscle regeneration after injury and maintenance of muscle mass with aging"
    explanation: >-
      Supports treating skeletal muscle as a TR-alpha-dependent tissue, which is
      why a THRA variant affects it.
- name: Impaired Central Nervous System Thyroid Hormone Action
  biological_scale: TISSUE
  description: >-
    The central nervous system is a major TR-alpha-dependent tissue, and
    developmental delay is the most frequent presenting problem in infancy:
    delayed motor and speech milestones in the large majority of reported
    infants, with intellectual outcome ranging from normal to moderate
    impairment and correlating with variant class. Adults diagnosed late
    describe reduced intellectual and learning abilities alongside tiredness
    and low mood.
  mechanism_confidence: ESTABLISHED
  cell_types:
  - preferred_term: central nervous system neuron
    term:
      id: CL:2000029
      label: central nervous system neuron
  biological_processes:
  - preferred_term: TR-alpha1-mediated thyroid hormone signaling in the central nervous system
    modifier: LOSS_OF_FUNCTION
    term:
      id: GO:0002154
      label: thyroid hormone receptor signaling pathway
  downstream:
  - target: Global developmental delay
    causal_link_type: DIRECT
  - target: Motor delay
    causal_link_type: DIRECT
  - target: Mild intellectual disability
    causal_link_type: DIRECT
  - target: Delayed speech and language development
    causal_link_type: DIRECT
  - target: Gait ataxia
    causal_link_type: DIRECT
  - target: Seizure
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Via abnormal development of GABAergic inhibitory interneurons, which is the
      intermediate the TR-alpha1 mutant mouse work identifies and to which the human
      epilepsy association is attributed.
  evidence:
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In infants with RTHα, delayed milestones for motor and speech abilities are the most common symptoms, noted in 34 among 40 cases (85%)"
    explanation: >-
      Quantifies developmental delay as the commonest infant presentation across
      the published cases.
  - reference: PMID:37469961
    reference_title: Clinical and Biochemical Characteristics of Untreated Adult Patients With Resistance to Thyroid Hormone Alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Delayed motor and language development and decreased intellectual and learning abilities were described."
    explanation: >-
      Documents the same neurodevelopmental domain in adults who were never
      treated, indicating it is not an artifact of early ascertainment.
phenotypes:
- name: Short stature
  category: Growth
  frequency: FREQUENT
  description: >-
    Disproportionate short stature with short limbs, metacarpals and phalanges,
    reported in about 60% of children with available data. Growth retardation was
    part of the index presentation and is one of the features that improves with
    levothyroxine in some patients.
  phenotype_term:
    preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  evidence:
  - reference: PMID:37469961
    reference_title: Clinical and Biochemical Characteristics of Untreated Adult Patients With Resistance to Thyroid Hormone Alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "During childhood and adolescence, short stature, short limbs, metacarpals, and phalanges, and delayed bone age maturation were observed."
    explanation: >-
      Reports short stature with disproportionate short limbs in four untreated
      adult patients, referencing their childhood and adolescent course.
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Short stature is one of the most common clinical findings in children with RTHα (12 among 20 children with available data, 60%)"
    explanation: >-
      Gives the paediatric frequency across published cases, which is what fixes
      this at FREQUENT rather than VERY_FREQUENT.
- name: Delayed skeletal maturation
  category: Skeletal
  frequency: FREQUENT
  description: >-
    Delayed bone age, a consistent childhood finding and one of the features
    that prompts skeletal imaging before the diagnosis is considered.
  phenotype_term:
    preferred_term: Delayed bone age
    term:
      id: HP:0002750
      label: Delayed skeletal maturation
  evidence:
  - reference: PMID:37469961
    reference_title: Clinical and Biochemical Characteristics of Untreated Adult Patients With Resistance to Thyroid Hormone Alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "During childhood and adolescence, short stature, short limbs, metacarpals, and phalanges, and delayed bone age maturation were observed."
    explanation: Records delayed bone age maturation during childhood and adolescence.
- name: Epiphyseal dysplasia
  category: Skeletal
  description: >-
    Epiphyseal dysgenesis, reported as a component of the skeletal dysplasia of
    RTH-alpha.
  phenotype_term:
    preferred_term: Epiphyseal dysgenesis
    term:
      id: HP:0002656
      label: Epiphyseal dysplasia
  evidence:
  - reference: PMID:26303090
    reference_title: Resistance to thyroid hormone due to defective thyroid receptor alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical features include dysmorphic facies, skeletal dysplasia (macrocephaly, epiphyseal dysgenesis), growth retardation, constipation, dyspraxia and intellectual deficit."
    explanation: Names epiphyseal dysgenesis as part of the skeletal dysplasia.
- name: Macrocephaly
  category: Skeletal
  frequency: FREQUENT
  description: >-
    Relatively increased head circumference, reported in about 70% of cases with
    available data - described both as macrocephaly within the skeletal dysplasia
    and as increased head circumference in untreated adults.
  phenotype_term:
    preferred_term: Macrocephaly
    term:
      id: HP:0000256
      label: Macrocephaly
  evidence:
  - reference: PMID:28471274
    reference_title: Contrasting Phenotypes in Resistance to Thyroid Hormone Alpha Correlate with Divergent Properties of Thyroid Hormone Receptor α1 Mutant Proteins.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Both individuals exhibited macrocephaly, delayed dentition, and constipation, together with a subnormal T4/triiodothyronine (T3) ratio, low reverse T3 levels, and mild anemia."
    explanation: >-
      Documents macrocephaly in both adolescents of a two-patient
      genotype-phenotype study, alongside the characteristic biochemistry.
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Macrocephalia is also a common clinical finding (23 among 33 cases with available data, 70%)"
    explanation: Gives the 70% frequency across published cases.
- name: Delayed eruption of teeth
  category: Skeletal
  frequency: FREQUENT
  description: >-
    Delayed dentition, reported in 44% of children with available data, and one of
    the features that significantly distinguished known RTH-alpha patients from
    biochemically similar children without a THRA variant.
  phenotype_term:
    preferred_term: Delayed dentition
    term:
      id: HP:0000684
      label: Delayed eruption of teeth
  evidence:
  - reference: PMID:38148509
    reference_title: Anaemia-based screening for resistance to thyroid hormone alpha in children.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Known RTH-α patients had significantly lower median height SD score, higher rates of delayed tooth eruption and closure of the anterior fontanelle, lower haemoglobin levels, and higher mean corpuscular volume (MCV) and CK levels as compared to those found without RTH-α."
    explanation: >-
      Delayed tooth eruption discriminated confirmed RTH-alpha patients from
      screened children without a THRA variant.
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Delayed tooth eruption was detected in eight among 18 children with available data (44%)"
    explanation: Gives the paediatric frequency behind the FREQUENT classification.
- name: Delayed closure of the anterior fontanelle
  category: Skeletal
  description: >-
    Delayed anterior fontanelle closure, discriminating confirmed RTH-alpha
    patients from biochemically similar children in a screening study.
  phenotype_term:
    preferred_term: Delayed closure of the anterior fontanelle
    term:
      id: HP:0001476
      label: Delayed closure of the anterior fontanelle
  evidence:
  - reference: PMID:38148509
    reference_title: Anaemia-based screening for resistance to thyroid hormone alpha in children.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Known RTH-α patients had significantly lower median height SD score, higher rates of delayed tooth eruption and closure of the anterior fontanelle, lower haemoglobin levels, and higher mean corpuscular volume (MCV) and CK levels as compared to those found without RTH-α."
    explanation: >-
      Reports delayed fontanelle closure at a significantly higher rate in
      confirmed RTH-alpha patients.
- name: Coarse facial features
  category: Craniofacial
  description: >-
    A round, somewhat coarse and flat face, described consistently across
    cohorts as part of the recognizable RTH-alpha gestalt.
  phenotype_term:
    preferred_term: Round, coarse, flat facies
    term:
      id: HP:0000280
      label: Coarse facial features
  evidence:
  - reference: PMID:25670821
    reference_title: Thyroid hormone resistance syndrome due to mutations in the thyroid hormone receptor α gene (THRA).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a distinct and consistent phenotype of mild hypothyroidism (growth retardation, relatively high birth length and weight, mild-to-moderate mental retardation, mild skeletal dysplasia and constipation), specific facial features (round, somewhat coarse and flat face) and macrocephaly"
    explanation: >-
      Describes the facial phenotype explicitly as round, somewhat coarse and
      flat, in a six-patient cohort followed for 18 years.
- name: Constipation
  category: Gastrointestinal
  frequency: VERY_FREQUENT
  description: >-
    Severe, often lifelong constipation reported in roughly 84% of published
    cases independent of age. It was one of the features of the index case and
    is the feature most reliably relieved by levothyroxine.
  phenotype_term:
    preferred_term: Constipation
    term:
      id: HP:0002019
      label: Constipation
    temporality: CHRONIC
  evidence:
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Independent of age, constipation is one of the most common clinical symptoms in human cases, being reported in 26 among 31 cases with available data (84%)"
    explanation: >-
      Gives the 84% frequency across published cases, supporting the
      VERY_FREQUENT classification.
- name: Anemia
  category: Hematologic
  frequency: FREQUENT
  description: >-
    Normocytic or macrocytic anaemia, present in about 77% of published cases
    and among the most consistent laboratory abnormalities. Mean corpuscular
    volume is characteristically higher in RTH-alpha patients than in
    biochemically similar children without a THRA variant. Unlike constipation,
    anaemia frequently persists on levothyroxine.
  phenotype_term:
    preferred_term: Normocytic or macrocytic anaemia
    term:
      id: HP:0001903
      label: Anemia
  evidence:
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In humans, 23 among 30 cases with available data (77%) had anemia, and it has been one of the most common findings in humans with RTHα"
    explanation: Gives the anaemia frequency across published cases.
  - reference: PMID:36821077
    reference_title: Long-term follow-up results and treatment outcomes of children and adults with resistance to thyroid hormone alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Anemia was present in five patients at diagnosis, which resolved in one adult patient but occurred in one child despite treatment"
    explanation: >-
      Shows that anaemia is present at diagnosis and largely persists on
      levothyroxine, which is why it is not curated as a treatment-responsive
      feature.
- name: Bradycardia
  category: Cardiovascular
  frequency: OCCASIONAL
  description: >-
    Bradycardia is reported in a minority of patients, most having a normal
    heart rate. Its mechanistic interest is disproportionate to its frequency:
    in TR-alpha1 mutant mice it is intrinsic to the heart, and in patients it
    does not correct on thyroxine, which is what makes high-dose thyroxine
    tolerable in this disorder.
  phenotype_term:
    preferred_term: Bradycardia
    term:
      id: HP:0001662
      label: Bradycardia
  evidence:
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Although most of the patients had normal heart rate or blood pressure, some cases were reported to have bradycardia"
    explanation: >-
      Supports OCCASIONAL rather than a higher frequency: most reported patients
      have a normal heart rate.
- name: Elevated circulating creatine kinase concentration
  category: Musculoskeletal
  frequency: FREQUENT
  description: >-
    Mildly raised serum creatine kinase, particularly in children. It is one of
    the few laboratory abnormalities outside the thyroid panel that should
    prompt THRA sequencing, and it falls measurably on levothyroxine.
  phenotype_term:
    preferred_term: Raised muscle creatine kinase
    term:
      id: HP:0003236
      label: Elevated circulating creatine kinase activity
  evidence:
  - reference: PMID:26303090
    reference_title: Resistance to thyroid hormone due to defective thyroid receptor alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Biochemical abnormalities include low/low-normal T4 and high/high-normal T3 concentrations, a subnormal T4/T3 ratio, variably reduced reverse T3, raised muscle creatine kinase and mild anaemia."
    explanation: Lists raised muscle creatine kinase among the biochemical abnormalities.
- name: Global developmental delay
  category: Neurodevelopmental
  frequency: VERY_FREQUENT
  description: >-
    Delayed motor and speech milestones are the commonest presentation in
    infancy, reported in 85% of published cases. This is usually the reason the
    child reaches medical attention at all, given that newborn screening does
    not detect the disorder.
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In infants with RTHα, delayed milestones for motor and speech abilities are the most common symptoms, noted in 34 among 40 cases (85%)"
    explanation: Gives the 85% frequency supporting VERY_FREQUENT.
- name: Motor delay
  category: Neurodevelopmental
  description: >-
    Delayed gross and fine motor development, including dyspraxia, documented in
    both children and untreated adults.
  phenotype_term:
    preferred_term: Delayed motor development
    term:
      id: HP:0001270
      label: Motor delay
  evidence:
  - reference: PMID:37469961
    reference_title: Clinical and Biochemical Characteristics of Untreated Adult Patients With Resistance to Thyroid Hormone Alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Delayed motor and language development and decreased intellectual and learning abilities were described."
    explanation: Records delayed motor development in four untreated adult patients.
- name: Mild intellectual disability
  category: Neurodevelopmental
  description: >-
    Intellectual outcome ranges from normal to moderate impairment and tracks
    variant class, with truncating variants producing the more severe
    phenotypes. Mild-to-moderate impairment is the usual finding.
  phenotype_term:
    preferred_term: Mild-to-moderate intellectual impairment
    term:
      id: HP:0001256
      label: Mild intellectual disability
  evidence:
  - reference: PMID:25670821
    reference_title: Thyroid hormone resistance syndrome due to mutations in the thyroid hormone receptor α gene (THRA).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a distinct and consistent phenotype of mild hypothyroidism (growth retardation, relatively high birth length and weight, mild-to-moderate mental retardation, mild skeletal dysplasia and constipation), specific facial features (round, somewhat coarse and flat face) and macrocephaly"
    explanation: >-
      Describes mild-to-moderate cognitive impairment as part of the consistent
      phenotype. The source's term "mental retardation" reflects 2015 usage and
      is quoted unaltered.
- name: Hypercholesterolemia
  category: Metabolic
  description: >-
    Mildly elevated cholesterol, with a raised LDL/HDL ratio in untreated
    adults - a TR-beta-dependent readout that is nonetheless abnormal here,
    which is worth noting because it complicates the otherwise clean
    TR-alpha/TR-beta division. No pathophysiology node is claimed upstream of
    this phenotype: cholesterol handling is hepatic and therefore TR-beta
    territory, so the route by which a THRA variant raises it is not accounted
    for by any node here, and nothing located explains it. Left deliberately
    unconnected rather than attached to a node it does not follow from.
  phenotype_term:
    preferred_term: Elevated cholesterol with raised LDL/HDL ratio
    term:
      id: HP:0003124
      label: Hypercholesterolemia
  evidence:
  - reference: PMID:25670821
    reference_title: Thyroid hormone resistance syndrome due to mutations in the thyroid hormone receptor α gene (THRA).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Laboratory investigations revealed anaemia and slightly elevated cholesterol"
    explanation: Reports slightly elevated cholesterol in the cohort.
  - reference: PMID:37469961
    reference_title: Clinical and Biochemical Characteristics of Untreated Adult Patients With Resistance to Thyroid Hormone Alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other main features were low hemoglobin and high LDL/HDL ratio."
    explanation: Documents the raised LDL/HDL ratio in untreated adults.
- name: Wormian bones
  category: Skeletal
  frequency: FREQUENT
  description: >-
    Wormian bones in the skull sutures, reported in 32% of cases with available
    data - part of the same delayed cranial ossification that produces the
    relatively large head and the late fontanelle closure.
  phenotype_term:
    preferred_term: Wormian bones in skull sutures
    term:
      id: HP:0002645
      label: Wormian bones
  evidence:
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Wormian bones in skull sutures were present in 10 among 31 cases with available data (32%)"
    explanation: Gives the frequency across published cases with skull imaging.
- name: Cranial hyperostosis
  category: Skeletal
  description: >-
    Thickened calvarium on skull radiography. Reported qualitatively ("in some
    patients") rather than with a frequency, so no frequency is assigned.
  phenotype_term:
    preferred_term: Cranial hyperostosis on skull radiography
    term:
      id: HP:0004437
      label: Cranial hyperostosis
  notes: >-
    A deep-research lead described thickened calvarium together with "increased
    bone mineral density" as characteristic in adults. The bone-density half does
    not hold up: the same review reports bone mineral density as normal in the
    three adult patients in whom it was measured, so only the hyperostosis is
    curated here.
  evidence:
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Skull radiography showed cranial hyperostosis in some patients"
    explanation: >-
      Supports the radiographic finding, and its hedged wording is why no
      frequency is recorded.
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "Bone mineral density was reported to be normal in three adult patients"
    explanation: >-
      Refutes the accompanying claim that bone mineral density is increased in
      adult RTH-alpha. Recorded rather than dropped, because the expectation is a
      reasonable one and a reader should see that it was checked and failed.
- name: Skin tags
  category: Dermatologic
  frequency: OCCASIONAL
  description: >-
    Skin tags, reported in 21% of cases with available data and described as more
    prominent in adults.
  phenotype_term:
    preferred_term: Skin tags
    term:
      id: HP:0010609
      label: Skin tags
  notes: >-
    Bound to HP:0010609. A deep-research lead offered HP:0010701 for this
    phenotype; that identifier is Abnormal circulating immunoglobulin
    concentration, confirmed by direct lookup against ols:hp, and the report's own
    Term Validation section flagged it. The correct term was found independently.
  evidence:
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Skin tags were present in 21% of cases with RTHα; seven among 33 cases with available data"
    explanation: Gives the frequency behind the OCCASIONAL classification.
- name: Delayed speech and language development
  category: Neurodevelopmental
  frequency: FREQUENT
  description: >-
    Speech delay with dysarthric or slow speech, described as a significant
    disability seen in the majority of cases and persisting into adulthood in the
    untreated.
  phenotype_term:
    preferred_term: Speech delay with dysarthric or slow speech
    term:
      id: HP:0000750
      label: Delayed speech and language development
  evidence:
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Speech delay and dysarthric or slow speech are significant disabilities and are seen in the majority of cases"
    explanation: >-
      States that speech involvement is seen in the majority and is disabling,
      which is what distinguishes it from the general developmental delay entry.
  - reference: PMID:42301959
    reference_title: "Intrafamilial and Age-Dependent Variability in Resistance to Thyroid Hormone Alpha: A Case Report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Both sisters exhibited normocytic anemia and delayed language development."
    explanation: >-
      Independent confirmation in a 2026 three-member kindred, alongside the
      anaemia.
- name: Gait ataxia
  category: Neurologic
  description: >-
    Motor discoordination with dyspraxia, ataxia and a broad or unstable gait, on
    neurological examination. Reported as a major source of disability across ages
    and one of the domains that improves on levothyroxine in some patients.
  phenotype_term:
    preferred_term: Dyspraxia with ataxia and broad or unstable gait
    term:
      id: HP:0002066
      label: Gait ataxia
  evidence:
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "evident motor discoordination including dyspraxia, ataxia, and broad or unstable gait are some of the clinical findings on neurological examination"
    explanation: >-
      Names the motor signs found on examination, which is the basis for curating
      a gait phenotype distinct from the milestone delay.
- name: Seizure
  category: Neurologic
  frequency: OCCASIONAL
  description: >-
    Epilepsy in a minority of reported cases. Mechanistically interesting out of
    proportion to its frequency, because TR-alpha1 mutant mice show abnormal
    GABAergic interneuron development together with stimulus-induced seizures.
  phenotype_term:
    preferred_term: Epilepsy
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Seizures after stimulation with light or audio and abnormal evolution of GABAergic neurons in TRα1 mutant mice correlated with epilepsy in human cases"
    explanation: >-
      Records epilepsy in human cases and links it to the GABAergic interneuron
      defect of the mouse model. Graded HUMAN_CLINICAL because the sentence is a
      review's statement about the human cases; the mouse half of the same
      sentence is what the animal_models links cite separately.
- name: Hepatic steatosis
  category: Gastrointestinal
  description: >-
    Hepatic steatosis, reported in adult carriers. Worth noting because hepatic
    lipid handling is largely TR-beta territory, so like the raised cholesterol it
    sits awkwardly with a purely TR-alpha account of the disorder.
  phenotype_term:
    preferred_term: Hepatic steatosis
    term:
      id: HP:0001397
      label: Hepatic steatosis
  notes: >-
    No pathophysiology node is claimed upstream, for the same reason as
    Hypercholesterolemia: the liver is a TR-beta-dependent tissue and nothing
    located explains how a THRA variant produces steatosis.
  evidence:
  - reference: PMID:42301959
    reference_title: "Intrafamilial and Age-Dependent Variability in Resistance to Thyroid Hormone Alpha: A Case Report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Additional clinical features included variably present delayed dentition, chronic constipation, and hepatic steatosis."
    explanation: >-
      Documents hepatic steatosis in a THRA kindred, and its own "variably
      present" wording is why no frequency is assigned.
biochemical:
- name: Serum Free Thyroxine (Free T4)
  presence: DECREASED
  biomarker_term:
    preferred_term: free thyroxine measurement
    term:
      id: NCIT:C74786
      label: Free Thyroxine Measurement
  notes: >-
    Free T4 is low or in the lower half of the reference interval - not
    necessarily frankly low, which is why it is unreliable on its own. In the
    untreated adult series, free T4 was within the reference range in all four
    patients. The 0.8-1.8 ng/dL band below is a conventional clinical laboratory
    reference interval with no single citable primary source (assay- and
    age-dependent), recorded here per the convention used in
    Generalized_Resistance_to_Thyroid_Hormone and Allan-Herndon-Dudley_Syndrome
    rather than attributed to a fabricated citation. No RTH-alpha cohort mean or
    median free T4 is asserted: the only large set of values located
    (PMID:38148509) is the median for children selected by the screening filter,
    and no THRA variant was found in any of them, so those numbers describe the
    filter's catchment rather than the disease.
  reference_ranges:
  - loinc_term:
      id: LOINC:3024-7
      label: Thyroxine (T4) free [Mass/volume] in Serum or Plasma
    lower_bound: 0.8
    upper_bound: 1.8
    unit: ng/dL
    population: Children and adults; conventional clinical laboratory interval, assay- and age-dependent.
    notes: >-
      Conventional clinical laboratory interval, recorded rather than cited.
      LOINC:3024-7 was resolved against the NLM Clinical Table Search Service on
      2026-09-10; LOINC is not configured in conf/oak_config.yaml, so this code
      is not covered by just validate-terms.
  evidence:
  - reference: PMID:28527577
    reference_title: Resistance to Thyroid Hormone due to Heterozygous Mutations in Thyroid Hormone Receptor Alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In addition, serum (F)T3 levels can be high-normal to high, (F)T4 and rT3 levels normal to low, while TSH is normal or mildly raised."
    explanation: >-
      States the free T4 direction (normal to low) within the full discordant
      profile.
  - reference: PMID:37469961
    reference_title: Clinical and Biochemical Characteristics of Untreated Adult Patients With Resistance to Thyroid Hormone Alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "While thyrotropin (TSH) and free thyroxine (FT4) were within the reference range, free triiodothyronine (FT3) was high. FT4/FT3 ratio and reverse T3 were low."
    explanation: >-
      Shows that free T4 can sit entirely within the reference range in adults,
      which is the practical reason the single analyte is not diagnostic.
- name: Serum Free Triiodothyronine (Free T3)
  presence: INCREASED
  biomarker_term:
    preferred_term: free triiodothyronine measurement
    term:
      id: NCIT:C74787
      label: Free Triiodothyronine Measurement
  notes: >-
    Free T3 sits in the upper half of the reference interval or is frankly high.
    The 2.3-4.2 pg/mL band below is a conventional clinical laboratory interval
    recorded rather than cited, per the same convention as free T4 above. As with
    free T4, no RTH-alpha cohort value is asserted - the medians reported in
    PMID:38148509 belong to children selected by its screening filter, none of
    whom carried a THRA variant.
  reference_ranges:
  - loinc_term:
      id: LOINC:3051-0
      label: Triiodothyronine (T3) Free [Mass/volume] in Serum or Plasma
    lower_bound: 2.3
    upper_bound: 4.2
    unit: pg/mL
    population: Children and adults; conventional clinical laboratory interval, assay- and age-dependent.
    notes: >-
      Conventional clinical laboratory interval, recorded rather than cited.
      LOINC:3051-0 was resolved against the NLM Clinical Table Search Service on
      2026-09-10.
  evidence:
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Free triiodothyronine (T3) levels are in the upper half of normal range or frankly high and free thyroxine (T4) levels are low or in the lower half of normal range."
    explanation: >-
      States both directions and, crucially, that each can remain inside its
      reference interval.
- name: Serum Thyroid-Stimulating Hormone (TSH)
  presence: NORMAL
  biomarker_term:
    preferred_term: serum thyroid-stimulating hormone
    term:
      id: NCIT:C2280
      label: Thyroid-Stimulating Hormone
  notes: >-
    The defining negative finding. TSH is normal or at most mildly raised
    despite tissue hypothyroidism, because the pituitary thyrotroph signals
    through TR-beta2 and is unaffected. This is what separates RTH-alpha from
    primary and congenital hypothyroidism and what makes TSH-based newborn
    screening blind to it. NCIT has no "Thyroid Stimulating Hormone
    Measurement" term analogous to NCIT:C74786 and NCIT:C74787, so the analyte
    term NCIT:C2280 is bound instead; searches of ols:ncit for "Thyrotropin",
    "Thyroid Stimulating Hormone" and "TSH" on 2026-09-10 returned no
    measurement term. The 0.4-4.0 mU/L band is a conventional clinical
    laboratory interval recorded rather than cited.
  reference_ranges:
  - loinc_term:
      id: LOINC:3016-3
      label: Thyrotropin [Units/volume] in Serum or Plasma
    lower_bound: 0.4
    upper_bound: 4.0
    unit: mU/L
    population: Children and adults; conventional clinical laboratory interval, assay-dependent.
    notes: >-
      Conventional clinical laboratory interval, recorded rather than cited. The
      RTH-alpha-specific point is not where the interval lies but that patients
      fall inside it.
    interpretation_bands:
    - name: Inappropriately normal TSH for the degree of tissue hypothyroidism
      lower_bound: 0.4
      upper_bound: 4.0
      unit: mU/L
      abnormal_flag: NORMAL
      phenotype_term:
        preferred_term: Inappropriately normal TSH despite tissue hypothyroidism
        term:
          id: HP:0033075
          label: Inappropriately normal thyroid-stimulating hormone level
      interpretation: >-
        A TSH inside the reference interval in a child with growth retardation,
        delayed bone age, constipation and anaemia does not exclude a disorder of
        thyroid hormone action; in RTH-alpha it is the expected result. Reading
        it as reassurance is the commonest route to diagnostic delay.
  evidence:
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Many symptoms and findings are similar to those seen in primary hypothyroidism. However, thyroid-stimulating hormone levels are normal."
    explanation: >-
      States the dissociation in one sentence: a hypothyroid clinical picture
      with a normal TSH.
- name: Serum Reverse T3
  presence: DECREASED
  biomarker_term:
    preferred_term: reverse triiodothyronine measurement
    term:
      id: NCIT:C81968
      label: Reverse Triiodothyronine Measurement
  notes: >-
    Low reverse T3 is one of the few discriminating analytes outside the
    standard thyroid panel and is specifically named as a finding that should
    prompt THRA sequencing. It is variably rather than invariably reduced. No
    reference interval is recorded here because nothing located gives a citable
    one for reverse T3 in children, and assay availability is itself a practical
    barrier.
  reference_ranges:
  - loinc_term:
      id: LOINC:3052-8
      label: Triiodothyronine (T3).reverse [Mass/volume] in Serum or Plasma
    population: Not specified - the analyte is bound for machine-queryability; no reference interval is asserted.
    notes: >-
      Bounds are deliberately omitted. LOINC:3052-8 was resolved against the NLM
      Clinical Table Search Service on 2026-09-10.
  evidence:
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In such patients, low reverse T3 levels, normo- or macrocytic anemia or, particularly in children, mildly elevated creatine kinase levels would warrant THRA sequencing."
    explanation: >-
      Names low reverse T3 as one of three findings that should trigger THRA
      sequencing.
  - reference: PMID:26303090
    reference_title: Resistance to thyroid hormone due to defective thyroid receptor alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Biochemical abnormalities include low/low-normal T4 and high/high-normal T3 concentrations, a subnormal T4/T3 ratio, variably reduced reverse T3, raised muscle creatine kinase and mild anaemia."
    explanation: >-
      Qualifies reverse T3 as variably reduced rather than uniformly low, which
      is why it is a supporting and not a defining finding.
- name: Free T4 to Free T3 Ratio
  presence: DECREASED
  notes: >-
    The practical discriminator, and the reason it is curated as its own entry
    rather than left implicit. Note that the literature states this ratio in both
    orientations and they are reciprocals, not disagreements: a subnormal or low
    T4/T3 (or FT4/FT3) ratio is the same finding as an elevated T3/T4 (or
    fT3/fT4) ratio. This record uses the free T4 over free T3 orientation, hence
    presence: DECREASED; the third definitions entry uses the fT3/fT4 orientation
    because that is how its source's centile charts are published. The point is: free T4 and free T3 can each lie inside their
    reference intervals while their ratio is clearly abnormal. Sex-specific
    fT3/fT4 centile charts derived from 23,522 data points separate genetically
    confirmed thyroid hormone resistance patients - including THRA cases - from
    both normal children and children with severe cerebral palsy. No
    biomarker_term is bound: NCIT:C181446 is a thyrotropin-to-free-thyroxine
    ratio, not this ratio, and searches of ols:ncit on 2026-09-10 found no term
    for a free T4 to free T3 or free T3 to free T4 ratio. No loinc_term is bound
    for the same reason - LOINC:57899-7 is the T3-to-reverse-T3 ratio.
  evidence:
  - reference: PMID:39201272
    reference_title: "Normal Values for the fT3/fT4 Ratio: Centile Charts (0-29 Years) and Their Application for the Differential Diagnosis of Children with Developmental Delay."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we were able to demonstrate a clear separation of patient values for the fT3/fT4 ratio from normal and pathological controls"
    explanation: >-
      Demonstrates that the ratio separates confirmed thyroid hormone resistance
      patients from both normal and disease controls, which is the basis for
      treating it as the discriminating measurement.
  - reference: PMID:25670821
    reference_title: Thyroid hormone resistance syndrome due to mutations in the thyroid hormone receptor α gene (THRA).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the thyroid profile showed low free thyroxine (fT4) levels coupled with high free T3 (fT3), leading to an altered T4 : T3 ratio, along with normal thyroid-stimulating hormone levels"
    explanation: >-
      Reports the altered T4:T3 ratio as the composite abnormality arising from
      the two individually unremarkable analytes.
- name: Serum Creatine Kinase
  presence: INCREASED
  biomarker_term:
    preferred_term: creatine kinase measurement
    term:
      id: NCIT:C64489
      label: Creatine Kinase Measurement
  notes: >-
    Mildly raised, particularly in children, and higher in confirmed RTH-alpha
    patients than in biochemically similar children without a THRA variant. It
    falls measurably on levothyroxine, making it one of the few available
    pharmacodynamic readouts in this disorder. No reference interval is recorded
    because the cited sources report values relative to each laboratory's own
    upper limit rather than an interval.
  reference_ranges:
  - loinc_term:
      id: LOINC:2157-6
      label: Creatine kinase [Enzymatic activity/volume] in Serum or Plasma
    population: Not specified - the analyte is bound for machine-queryability; no reference interval is asserted.
    notes: >-
      Bounds deliberately omitted. LOINC:2157-6 was resolved against the NLM
      Clinical Table Search Service on 2026-09-10.
  readouts:
  - target: treatments#Levothyroxine
    relationship: PHARMACODYNAMIC_MARKER_OF
    direction: NEGATIVE
    interpretation: >-
      Creatine kinase expressed as a fraction of the laboratory's reference upper
      limit fell from a median of 1.3 before treatment to 0.9 at the final visit
      in a seven-patient cohort treated for a median of 6.7 years.
    evidence:
    - reference: PMID:36821077
      reference_title: Long-term follow-up results and treatment outcomes of children and adults with resistance to thyroid hormone alpha.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "At the final visit, creatine kinase levels relative to the reference upper limit were significantly lower compared to the pre-treatment ratios"
      explanation: >-
        Reports the treatment-associated fall in creatine kinase, which is what
        makes it a pharmacodynamic marker of levothyroxine here.
  evidence:
  - reference: PMID:38148509
    reference_title: Anaemia-based screening for resistance to thyroid hormone alpha in children.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Known RTH-α patients had significantly lower median height SD score, higher rates of delayed tooth eruption and closure of the anterior fontanelle, lower haemoglobin levels, and higher mean corpuscular volume (MCV) and CK levels as compared to those found without RTH-α."
    explanation: >-
      Shows creatine kinase is significantly higher in confirmed RTH-alpha
      patients than in biochemically similar children without a THRA variant.
- name: Haemoglobin and Mean Corpuscular Volume
  presence: ABNORMAL
  biomarker_term:
    preferred_term: haemoglobin measurement
    term:
      id: NCIT:C64848
      label: Hemoglobin Measurement
  notes: >-
    Low haemoglobin with a normal or raised mean corpuscular volume - normocytic
    or macrocytic anaemia, never microcytic, which is what makes it usable as a
    screening signal in a paediatric neurology population. Haemoglobin and MCV
    are curated as one entry because it is the combination, not either value,
    that carries the signal. No reference intervals are recorded: both are
    strongly age-dependent in children and nothing located gives a citable
    paediatric interval for this purpose.
  reference_ranges:
  - loinc_term:
      id: LOINC:718-7
      label: Hemoglobin [Mass/volume] in Blood
    population: Not specified - strongly age-dependent in children; no interval asserted.
    notes: >-
      Bounds deliberately omitted. LOINC:718-7 was resolved against the NLM
      Clinical Table Search Service on 2026-09-10.
  - loinc_term:
      id: LOINC:787-2
      label: MCV [Entitic mean volume] in Red Blood Cells by Automated count
    population: Not specified - strongly age-dependent in children; no interval asserted.
    notes: >-
      Bounds deliberately omitted. LOINC:787-2 was resolved against the NLM
      Clinical Table Search Service on 2026-09-10.
  evidence:
  - reference: PMID:38148509
    reference_title: Anaemia-based screening for resistance to thyroid hormone alpha in children.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "normo- or macrocytic anaemia, normal TSH levels, fT3 levels in the upper half of the normal range or high, and fT4 levels in the lower half of the normal range or low"
    explanation: >-
      Specifies the haematological pattern - normocytic or macrocytic, not
      microcytic - as used in an actual screening filter.
definitions:
- name: RTH-alpha biochemical and clinical suspicion criteria
  definition_type: DIAGNOSTIC_CRITERIA
  derivation_basis: ESTABLISHED_CRITERIA
  scope: Children and adults under investigation for unexplained hypothyroid features
  description: >-
    RTH-alpha should be suspected when even mild clinical features of
    hypothyroidism coexist with high or high-normal free T3, low or low-normal
    free T4, and a normal TSH, and confirmed by THRA sequencing. Low reverse T3,
    normocytic or macrocytic anaemia, and a mildly raised creatine kinase -
    particularly in a child - each independently justify sequencing even when
    the thyroid panel looks unremarkable.
  inclusion_criteria:
  - preferred_term: Clinical features of hypothyroidism, even mild
  - preferred_term: Free T3 high or high-normal
  - preferred_term: Free T4 low or low-normal
  - preferred_term: TSH normal or at most mildly raised
  - preferred_term: Pathogenic heterozygous THRA variant on sequencing
  evidence:
  - reference: PMID:28527577
    reference_title: Resistance to Thyroid Hormone due to Heterozygous Mutations in Thyroid Hormone Receptor Alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "RTHα should be suspected in subjects with even mild clinical features of hypothyroidism together with high/high-normal (F)T3, low/low-normal (F)T4, and normal TSH."
    explanation: States the suspicion criteria essentially verbatim.
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In such patients, low reverse T3 levels, normo- or macrocytic anemia or, particularly in children, mildly elevated creatine kinase levels would warrant THRA sequencing."
    explanation: Supplies the three additional findings that independently warrant sequencing.
- name: Anaemia-based paediatric screening filter for RTH-alpha
  definition_type: PHENOTYPE_ALGORITHM
  derivation_basis: ESTABLISHED_CRITERIA
  scope: Children attending paediatric neurology with anaemia and no specific neurological aetiology
  description: >-
    A computable case-finding filter applied to children seen in paediatric
    neurology: complete blood count and thyroid function tests in all, then
    select those with normocytic or macrocytic anaemia, a normal TSH, free T3 in
    the upper half of the reference range or high, and free T4 in the lower half
    of the reference range or low, excluding children with an identified
    neurological aetiology. Selected children proceed to THRA sequencing. The
    filter is built entirely from the established biochemical and haematological
    signature rather than from an unproven mechanism, hence
    ESTABLISHED_CRITERIA.
  inclusion_criteria:
  - preferred_term: Attending paediatric neurology with no specific underlying neurological aetiology
  - preferred_term: Normocytic or macrocytic anaemia on complete blood count
  - preferred_term: Normal TSH
  - preferred_term: Free T3 in the upper half of the reference range or high
  - preferred_term: Free T4 in the lower half of the reference range or low
  validation_status:
    status: UNVALIDATED
    rationale: >-
      Prospectively applied to 6,540 children evaluated in paediatric neurology
      outpatient clinics over two years. 432 had anaemia; 42 met the full filter;
      32 were sequenced. No new THRA variant was found, and the only RTH-alpha
      patient recovered was one already known. The filter therefore has no
      demonstrated positive predictive value in this setting. The authors'
      own conclusion is that the filter should be tightened with clinical
      features rather than used on laboratory criteria alone, because nearly half
      the screened children's anaemia did not persist on reassessment. Recorded
      as UNVALIDATED rather than PROPOSED because it has actually been run, and
      not as VALIDATED_AGAINST_GOLD_STANDARD because the run was negative.
    evidence:
    - reference: PMID:38148509
      reference_title: Anaemia-based screening for resistance to thyroid hormone alpha in children.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "This approach found one known patient with RTH-α but did not reveal any new cases."
      explanation: >-
        The negative result of the one prospective evaluation of this filter,
        which is what fixes the validation status.
    - reference: PMID:38148509
      reference_title: Anaemia-based screening for resistance to thyroid hormone alpha in children.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "A screening strategy that takes clinical findings and prominent laboratory features suggestive of RTH-α into account could lower unnecessary genetic analysis of THRA in patients presenting with neurological problems."
      explanation: >-
        The authors' recommendation to add clinical features to the laboratory
        filter, recorded here so the algorithm is not reused as-is.
  evidence:
  - reference: PMID:38148509
    reference_title: Anaemia-based screening for resistance to thyroid hormone alpha in children.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "normo- or macrocytic anaemia, normal TSH levels, fT3 levels in the upper half of the normal range or high, and fT4 levels in the lower half of the normal range or low"
    explanation: The laboratory selection criteria of the filter, as operationalized.
- name: fT3/fT4 ratio centile screening in children with developmental delay
  definition_type: PHENOTYPE_ALGORITHM
  derivation_basis: ESTABLISHED_CRITERIA
  scope: Children and young adults (0-29 years) with developmental delay
  description: >-
    Plot the free T3 to free T4 ratio on sex-specific centile charts derived from
    23,522 measurements in children and young adults, and treat an outlying ratio
    as an indication to investigate for a thyroid hormone resistance syndrome -
    MCT8 deficiency, THRA-related RTH-alpha, or SECISBP2 deficiency. The
    rationale is mechanistic but the mechanism is established, not hypothesized:
    each analyte may be within its reference interval while the ratio is not.
  inclusion_criteria:
  - preferred_term: Developmental delay under investigation
  - preferred_term: fT3/fT4 ratio outside the sex-specific reference centiles for age
  validation_status:
    status: PROPOSED
    rationale: >-
      Derived on a large normative cohort and shown to separate genetically
      confirmed MCT8, THRA and SECISBP2 patients from both normal children and
      children with severe cerebral palsy. That is a demonstration of separation
      in known cases, not a prospective case-finding evaluation, so no positive
      predictive value in an unselected developmental-delay population has been
      established and no THRA-specific cut-off is defined.
    evidence:
    - reference: PMID:39201272
      reference_title: "Normal Values for the fT3/fT4 Ratio: Centile Charts (0-29 Years) and Their Application for the Differential Diagnosis of Children with Developmental Delay."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "We therefore recommend using the fT3/fT4 ratio as a readily available screening parameter in children with developmental delay for the identification of thyroid hormone resistance syndromes."
      explanation: >-
        The recommendation itself, which is a proposal rather than a validated
        case-finding result.
  evidence:
  - reference: PMID:39201272
    reference_title: "Normal Values for the fT3/fT4 Ratio: Centile Charts (0-29 Years) and Their Application for the Differential Diagnosis of Children with Developmental Delay."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we were able to demonstrate a clear separation of patient values for the fT3/fT4 ratio from normal and pathological controls"
    explanation: >-
      The separation result on which the proposed screening use rests, including
      against a disease control group rather than only healthy children.
treatments:
- name: Levothyroxine
  description: >-
    Levothyroxine is the only treatment in routine use and there is no
    RTH-alpha-specific therapy. It is partial and tissue-selective for the same
    reason the disorder exists: raising circulating hormone can partly overcome
    resistance in tissues whose mutant receptor retains some T3 responsiveness,
    does nothing where the mutant is transcriptionally inert, and has no target
    to act on in TR-beta tissues that were never resistant. In practice it
    relieves constipation, lowers creatine kinase, and improves growth, body
    composition and dyspraxia in some patients, while anaemia commonly persists.
    Response tracks variant class: in a paired two-patient study the patient
    carrying the partially responsive A263V mutant improved in growth, body
    composition, dyspraxia and constipation, while the patient carrying the
    transcriptionally inert L274P mutant showed no change in growth retardation
    or constipation. The theoretical worry about inducing thyrotoxicosis in
    TR-beta tissues is not borne out for heart rate: thyroxine does not raise
    heart rate in RTH-alpha patients, because the cardiac defect is intrinsic to
    the heart and is not reversed by hormone given after birth, which is what
    makes higher dosing tolerable. (In the mouse the relevant gene expression
    could be restored by raising maternal T3 in utero, so "irreversible" here
    means irreversible postnatally, not in principle.)
  treatment_term:
    preferred_term: levothyroxine pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: levothyroxine
      term:
        id: CHEBI:18332
        label: L-thyroxine
  therapeutic_modality: SMALL_MOLECULE
  target_mechanisms:
  - target: Impaired Gastrointestinal Motility
    description: >-
      The most consistent treatment response: constipation was relieved in every
      patient who had it in a seven-patient cohort treated for a median of 6.7
      years.
    evidence:
    - reference: PMID:36821077
      reference_title: Long-term follow-up results and treatment outcomes of children and adults with resistance to thyroid hormone alpha.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Treatment ameliorated constipation in all patients with this complaint"
      explanation: >-
        Reports complete relief of constipation in all affected patients, which
        is the clearest evidence that this node is drug-reversible.
  - target: Impaired Skeletal Muscle Maintenance and Regeneration
    description: >-
      Creatine kinase fell significantly relative to the laboratory upper limit
      over a median 6.7 years of treatment, which is the available in-human
      pharmacodynamic evidence that the muscle node responds.
    evidence:
    - reference: PMID:36821077
      reference_title: Long-term follow-up results and treatment outcomes of children and adults with resistance to thyroid hormone alpha.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "At the final visit, creatine kinase levels relative to the reference upper limit were significantly lower compared to the pre-treatment ratios"
      explanation: Documents the fall in creatine kinase on treatment.
  - target: Impaired Central Nervous System Thyroid Hormone Action
    description: >-
      Partial and apparently age-dependent. IQ improved in most treated children,
      with the exception being the child diagnosed latest, at 9.5 years - which is
      the practical argument for early ascertainment rather than for the drug.
    evidence:
    - reference: PMID:36821077
      reference_title: Long-term follow-up results and treatment outcomes of children and adults with resistance to thyroid hormone alpha.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Normal mental functions were achieved and IQ scores improved in most children except one (age at diagnosis, 9.5 years)."
      explanation: >-
        Shows cognitive improvement in most treated children and names the
        exception by age at diagnosis, which is what supports the age-dependence
        rather than the uniform benefit.
  - target: Impaired Skeletal Maturation
    description: >-
      Variable and variant-dependent: growth improved in the patient with a
      partially T3-responsive mutant and was unchanged in the patient with a
      transcriptionally inert one.
    evidence:
    - reference: PMID:28471274
      reference_title: Contrasting Phenotypes in Resistance to Thyroid Hormone Alpha Correlate with Divergent Properties of Thyroid Hormone Receptor α1 Mutant Proteins.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Following T4 therapy, growth, body composition, dyspraxia, and constipation improved in P1, whereas growth retardation and constipation in P2 were unchanged."
      explanation: >-
        Directly contrasts the growth response between two patients whose mutant
        receptors differ in residual T3 responsiveness, which is why this edge is
        curated as variant-dependent rather than as a general benefit.
  - target: Reduced Intrinsic Cardiac Chronotropic Drive
    description: >-
      Recorded as a treatment target that does NOT respond. Thyroxine does not
      raise heart rate in RTH-alpha, because several heart-rate ion channel genes
      are irreversibly down-regulated while the pacemaker channels remain
      T3-responsive.
    evidence:
    - reference: PMID:37286550
      reference_title: Resistance to thyroid hormone induced tachycardia in RTHα syndrome.
      supports: REFUTE
      evidence_source: HUMAN_CLINICAL
      snippet: "Surprisingly, we report that treatment of RTHα patients with thyroxine to overcome tissue hormone resistance does not elevate their heart rate."
      explanation: >-
        Refutes the expectation that levothyroxine corrects, or conversely
        over-corrects, the cardiac node. Recorded as REFUTE on this edge rather
        than dropped, because a treatment target that provably does not respond
        is a substantive finding: it is the reason high-dose thyroxine is
        tolerable here.
  evidence:
  - reference: PMID:36821077
    reference_title: Long-term follow-up results and treatment outcomes of children and adults with resistance to thyroid hormone alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We demonstrated that constipation was ameliorated, neuromotor development of some children was improved, and creatine kinase levels were diminished with levothyroxine treatment in patients with RTHα, while some features including anemia did not resolve."
    explanation: >-
      The single best summary of what levothyroxine does and does not do in this
      disorder, including the explicit negative for anaemia.
  - reference: PMID:36821077
    reference_title: Long-term follow-up results and treatment outcomes of children and adults with resistance to thyroid hormone alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Resistance to thyroid hormone alpha (RTHα) is a rare entity and has no specific treatment."
    explanation: >-
      States that no disorder-specific treatment exists, which is why
      levothyroxine is curated as the only therapeutic entry.
  - reference: PMID:26303090
    reference_title: Resistance to thyroid hormone due to defective thyroid receptor alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "thyroxine therapy reverses some metabolic abnormalities and improves growth, constipation, dyspraxia and wellbeing"
    explanation: >-
      An independent statement of the partial benefit, naming the domains that
      respond.
- name: Genetic counselling
  description: >-
    RTH-alpha is autosomal dominant with a 50% transmission risk from an affected
    parent, and familial kindreds have been identified only after an index case
    was sequenced - in one series, four first-degree-related adults were
    diagnosed after a gene panel run on the index patient for intellectual
    disability. Counselling therefore doubles as a case-finding route for
    relatives who have reached adulthood undiagnosed.
  treatment_term:
    preferred_term: genetic counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:37469961
    reference_title: Clinical and Biochemical Characteristics of Untreated Adult Patients With Resistance to Thyroid Hormone Alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We investigated 4 previously untreated Caucasian adult first-degree-related patients with the THRA c.788C > T, p.(Ala263Val) variant identified by a gene panel for intellectual disability in the index patient."
    explanation: >-
      Documents the familial cascade: four related adults were identified only
      through the index patient's sequencing, which is the concrete yield of
      counselling and family testing here.
experimental_models:
- name: RTH-alpha patient primary erythroid progenitor cell culture
  experimental_model_type: PRIMARY_CELL_CULTURE
  description: >-
    Primary human erythroid progenitor cells expanded from the peripheral blood of
    11 RTH-alpha patients carrying seven different inactivating TR-alpha variants
    (P398R, F397fs406X, C392X, R384H, A382fs388X, A263V, A263S), compared with 11
    healthy controls, with maturation tracked by cell number, cell size, staining
    and flow cytometry over about 14 days of ex vivo expansion. This is the
    human-tissue counterpart of the Thra1PV/+ mouse erythroid work and the reason
    the erythroid node does not rest on animal data alone.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  cell_types:
  - preferred_term: erythroid progenitor cell
    term:
      id: CL:0000038
      label: erythroid progenitor cell
  cell_source: Peripheral blood of 11 genotyped RTH-alpha patients and 11 healthy controls
  culture_system: Ex vivo liquid expansion and differentiation culture of primary human erythroid progenitors
  publication: PMID:28911146
  modeled_mechanisms:
  - target: Impaired Terminal Erythroid Differentiation
    relationship: PARTIALLY_RECAPITULATES
    fidelity: HIGH
    model_scale: CELLULAR
    description: >-
      Patient-derived progenitors reproduce the erythroid maturation defect in
      human cells of the affected lineage, carrying the patients' own variants.
    limitations: >-
      PARTIALLY_RECAPITULATES rather than RECAPITULATES because the defect appears
      only in spontaneous differentiation: induced differentiation and T3 response
      were comparable to controls, so the culture does not reproduce a general
      inability to mature. The abnormality also did not correlate with the severity
      of the underlying TR-alpha defect, which means the system does not report
      genotype-phenotype gradation. Anaemia itself is an organism-level outcome and
      is not observed here.
    readouts:
    - name: Cell size and c-Kit positivity during spontaneous differentiation
      target: Impaired Terminal Erythroid Differentiation
      direction: INCREASED
      interpretation: >-
        Patient-derived progenitors stayed larger and more c-Kit-positive, i.e.
        held in a proliferative rather than maturing state.
      evidence:
      - reference: PMID:28911146
        reference_title: "Anemia in Patients With Resistance to Thyroid Hormone α: A Role for Thyroid Hormone Receptor α in Human Erythropoiesis."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "During spontaneous differentiation, RTHα-derived HEPs were larger, more positive for c-Kit (a proliferation marker), and less positive for glycophorin A (a differentiation marker)."
        explanation: The measured proliferation-marker and size readout.
    - name: Rate of spontaneous erythroid differentiation
      target: Impaired Terminal Erythroid Differentiation
      direction: DECREASED
      interpretation: >-
        Patient-derived progenitors differentiated more slowly than controls over
        the same ex vivo period.
      evidence:
      - reference: PMID:28911146
        reference_title: "Anemia in Patients With Resistance to Thyroid Hormone α: A Role for Thyroid Hormone Receptor α in Human Erythropoiesis."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "After ∼14 days of ex vivo expansion, both control and patient-derived progenitors differentiated spontaneously. However, RTHα-derived cells differentiated more slowly."
        explanation: The rate readout, including that differentiation still occurred.
    evidence:
    - reference: PMID:28911146
      reference_title: "Anemia in Patients With Resistance to Thyroid Hormone α: A Role for Thyroid Hormone Receptor α in Human Erythropoiesis."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Cultures of primary human erythroid progenitor cells (HEPs), from peripheral blood of RTHα patients (n = 11)"
      explanation: >-
        Establishes that the model is human, patient-derived, and of the affected
        lineage, which is what makes it informative for this node.
  notes: >-
    Recorded under experimental_models rather than animal_models because it is a
    non-animal human cell system, per the CLAUDE.md rule that experimental_models
    is for non-animal systems.
animal_models:
- name: Thra1PV/+ dominant-negative TR-alpha1 mouse
  species: Mouse
  genotype: Thra1PV/+ (frameshift TRalpha1PV mutant, heterozygous)
  publication: PMID:23610395
  description: >-
    A knock-in mouse expressing a frameshift TR-alpha1 mutant that shares its
    mutated C-terminal sequence with human THRA frameshift variants. Crossing it
    with the Ncor1-delta-ID mouse, whose NCOR1 cannot be recruited by the mutant
    receptor, partially reverses growth retardation, delayed bone development and
    infertility - which makes this the experiment that established corepressor
    recruitment as the operative mechanism in vivo rather than an in vitro
    inference.
  evidence:
  - reference: PMID:23610395
    reference_title: Nuclear receptor corepressor (NCOR1) regulates in vivo actions of a mutated thyroid hormone receptor α.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "TRα1PV shares the same C-terminal mutated sequences as those of patients with frameshift mutations of the THRA gene."
    explanation: >-
      Establishes this model's construct validity for human RTH-alpha: the mouse
      allele carries the same mutated C-terminal sequence as human THRA
      frameshift variants, rather than an arbitrary disruption of the gene.
  modeled_mechanisms:
  - target: Persistent Corepressor Occupancy at Thyroid Hormone Response Elements
    relationship: RECAPITULATES
    fidelity: HIGH
    model_scale: MOLECULAR
    description: >-
      The defining test: removing the mutant receptor's ability to recruit NCOR1
      relieves the phenotype, so the phenotype is a consequence of corepressor
      recruitment.
    limitations: >-
      The rescue arm uses a genetically engineered NCOR1 that cannot be recruited,
      not a pharmacological intervention, so it establishes mechanism without
      demonstrating a tractable human target. The rescue is also explicitly
      partial.
    evidence:
    - reference: PMID:23610395
      reference_title: Nuclear receptor corepressor (NCOR1) regulates in vivo actions of a mutated thyroid hormone receptor α.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Thus, the aberrant recruitment of NCOR1 by TRα1 mutants could lead to clinical hypothyroidism in humans."
      explanation: >-
        The authors' own conclusion that aberrant NCOR1 recruitment is the
        mechanism, which is the claim this link attests.
  - target: Impaired Skeletal Maturation
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    model_scale: ORGANISM
    description: >-
      Reproduces growth retardation and delayed bone development, both partially
      reversible by blocking NCOR1 recruitment.
    limitations: >-
      The mouse additionally shows infertility, which is not a reported feature of
      human RTH-alpha, so the phenotype is not a clean match; and the human
      skeletal picture includes epiphyseal dysgenesis and delayed dentition that
      the cited work does not assess.
    evidence:
    - reference: PMID:23610395
      reference_title: Nuclear receptor corepressor (NCOR1) regulates in vivo actions of a mutated thyroid hormone receptor α.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "The severe retarded growth, infertility, and delayed bone development were partially reverted in Thra1(PV/+) mice expressing NCOR1ΔID."
      explanation: >-
        Names the skeletal and growth phenotypes and their partial reversal,
        supporting PARTIALLY_RECAPITULATES rather than RECAPITULATES.
  - target: Impaired Terminal Erythroid Differentiation
    relationship: RECAPITULATES
    fidelity: HIGH
    model_scale: CELLULAR
    description: >-
      TR-alpha1PV directly suppresses key erythroid genes and impairs erythroid
      progenitor differentiation and terminal erythropoiesis; blocking NCOR1
      recruitment corrects both. The corresponding human feature - anaemia in
      about 77% of reported cases - is one of the commonest findings.
    limitations: >-
      The mouse rescue corrects erythroid differentiation, whereas human anaemia
      largely persists on levothyroxine. That is not a contradiction - the
      interventions differ - but it means the model's reversibility should not be
      read as predicting treatment response.
    evidence:
    - reference: PMID:29273766
      reference_title: NCOR1 modulates erythroid disorders caused by mutations of thyroid hormone receptor α1.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Thyroid hormone receptor α (THRA) gene mutations, via dominant negative mode, cause erythroid abnormalities in patients."
      explanation: >-
        Anchors the mouse erythroid work to the human erythroid phenotype,
        supporting this model as informative for the node.
- name: THRA-PV skeletal muscle model
  species: Mouse
  genotype: THRA-PV (frameshift THRA mutant)
  publication: PMID:33633251
  description: >-
    The same dominant-negative frameshift allele studied for skeletal muscle.
    Myoblasts show reduced proliferation and myogenic differentiation, muscle
    regeneration after cardiotoxin injury is impaired, and muscle mass is lost
    with age. The mechanism identified is persistent COUP-TFII (Nr2f2)
    expression, which interacts with TR-alpha and modulates its binding to
    thyroid hormone response elements; silencing COUP-TFII restores myogenic
    potential.
  evidence:
  - reference: PMID:33633251
    reference_title: Persistent COUP-TFII expression underlies the myopathy and impaired muscle regeneration observed in resistance to thyroid hormone-alpha.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Myoblasts derived from THRA-PV mice show reduced proliferation and myogenic differentiation in in vitro models"
    explanation: >-
      Supports treating this model as informative for skeletal muscle: the
      cellular defect is demonstrable in myoblasts derived from the mutant
      animals, not only at whole-muscle level.
  modeled_mechanisms:
  - target: Impaired Skeletal Muscle Maintenance and Regeneration
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: TISSUE
    description: >-
      Reproduces impaired regeneration after injury and age-associated muscle
      loss, and identifies a specific transcriptional intermediary.
    limitations: >-
      The human counterpart of this node is a mildly raised creatine kinase, not a
      documented regeneration failure or age-related sarcopenia, so the model is
      considerably more informative about the mechanism than about the human
      phenotype. Cardiotoxin-induced injury is also not a physiological human
      exposure.
    evidence:
    - reference: PMID:33633251
      reference_title: Persistent COUP-TFII expression underlies the myopathy and impaired muscle regeneration observed in resistance to thyroid hormone-alpha.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Silencing of COUP-TFII expression restores in vitro myogenic potential of THRA-PV myoblasts and shifts the mRNA expression profile closer to WT myoblasts."
      explanation: >-
        The rescue experiment identifying COUP-TFII as the intermediary, which is
        what makes this model informative for the muscle node rather than merely
        descriptive of it.
- name: TR-alpha1 mutant cardiac telemetry mouse
  species: Mouse
  genotype: TRalpha1 mutant (male)
  publication: PMID:37286550
  description: >-
    Cardiac telemetry in male TR-alpha1 mutant mice localized the bradycardia of
    RTH-alpha to the heart itself rather than to autonomic outflow, and
    transcriptomics showed preserved T3-dependent upregulation of the pacemaker
    channels Hcn2 and Hcn4 alongside irreversibly reduced expression of other
    heart-rate ion channel genes. Raising maternal T3 in utero restored that
    expression and the DNA methylation of Ryr2, implying a developmental window.
  evidence:
  - reference: PMID:37286550
    reference_title: Resistance to thyroid hormone induced tachycardia in RTHα syndrome.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Mutations in thyroid hormone receptor α1 (TRα1) cause Resistance to Thyroid Hormone α (RTHα), a disorder characterized by hypothyroidism in TRα1-expressing tissues including the heart."
    explanation: >-
      Frames the heart as one of the TR-alpha1-dependent tissues affected in
      RTH-alpha, which is what makes a TR-alpha1 mutant mouse the right system
      for the cardiac node.
  modeled_mechanisms:
  - target: Reduced Intrinsic Cardiac Chronotropic Drive
    relationship: RECAPITULATES
    fidelity: HIGH
    model_scale: TISSUE
    description: >-
      Reproduces the persistent bradycardia and demonstrates it is intrinsic to
      the heart, matching the clinical observation that thyroxine does not raise
      heart rate in patients.
    limitations: >-
      Only male mice were studied. The in utero maternal T3 rescue has no human
      counterpart - RTH-alpha is not diagnosed prenatally, precisely because there
      is no screening signal - so the developmental-window finding is not
      currently actionable.
    evidence:
    - reference: PMID:37286550
      reference_title: Resistance to thyroid hormone induced tachycardia in RTHα syndrome.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Transcriptomic analyses show preserved, thyroid hormone (T3)-dependent upregulation of pacemaker channels (Hcn2, Hcn4), but irreversibly reduced expression of several ion channel genes controlling heart rate."
      explanation: >-
        Identifies which cardiac target genes are and are not still T3-responsive,
        which is the mechanistic content of this link.
- name: thraa / thrab CRISPR dominant-negative zebrafish
  species: Zebrafish
  genotype: thrab 1-bp insertion and thraa 8-bp insertion dominant-negative alleles
  publication: PMID:31952464
  description: >-
    Germline-transmissible CRISPR/Cas9 dominant-negative alleles in the two
    duplicated zebrafish thra genes. Homozygous thrab mutants show severe growth
    retardation with markedly suppressed growth hormone and IGF1 expression,
    while homozygous thraa mutants are only mildly affected. The same species is
    the model in which the corepressor-dissociating ligand analogue ES08 rescued
    developmental anomalies.
  evidence:
  - reference: PMID:31952464
    reference_title: Generation of Novel Genetic Models to Dissect Resistance to Thyroid Hormone Receptor α in Zebrafish.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Using CRISPR/Cas9-mediated targeted mutagenesis, we created dominant negative mutations in the two duplicated thra genes."
    explanation: >-
      Records how the model was made, including that the engineered alleles are
      dominant-negative rather than null - the property that matters for
      comparability with human RTH-alpha - and that there are two paralogues,
      which is the property that limits it.
  modeled_mechanisms:
  - target: Impaired Skeletal Maturation
    relationship: PARTIALLY_RECAPITULATES
    fidelity: LOW
    model_scale: ORGANISM
    description: >-
      Reproduces severe postlarval growth retardation and identifies suppressed
      gh1 and igf1 expression as a proximate cause.
    limitations: >-
      Zebrafish have two thra paralogues where humans have one, and the phenotype
      partitions unequally between them, so the genotype is not comparable to a
      human heterozygote. The informative alleles are homozygous, whereas human
      RTH-alpha is heterozygous and dominant-negative. Zebrafish also have no
      growth plate, so endochondral ossification - the mechanism this node names -
      is not what is being observed.
    divergences:
    - divergence_type: SPECIES_MISMATCH
      materiality: QUALIFYING
      description: >-
        The thra locus is duplicated in zebrafish into thraa and thrab, and the
        growth phenotype is carried almost entirely by thrab. There is no single
        ortholog whose disruption corresponds to a human THRA heterozygote, so
        allele dosage and gene identity both diverge.
    - divergence_type: PROXY_QUANTITY
      materiality: QUALIFYING
      description: >-
        The measured quantity is body growth with gh1 and igf1 transcript levels.
        The node's quantity is growth plate chondrocyte maturation and
        endochondral ossification, which zebrafish do not have.
    evidence:
    - reference: PMID:31952464
      reference_title: Generation of Novel Genetic Models to Dissect Resistance to Thyroid Hormone Receptor α in Zebrafish.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Expression of the growth hormone (gh1) and insulin-like growth factor 1 was markedly suppressed in homozygous thrab 1-bp ins (m/m) mutants."
      explanation: >-
        Gives the molecular correlate of the growth phenotype in this model, which
        is what the link is citing it for.
- name: Low-T3-affinity TR-alpha1 knock-in mouse (TH rescue model)
  species: Mouse
  genotype: TRalpha1 knock-in with 10-fold reduced thyroid hormone affinity, heterozygous
  publication: PMID:16131613
  description: >-
    A heterozygous knock-in mouse whose TR-alpha1 binds thyroid hormone with
    10-fold lower affinity, producing extreme anxiety, reduced recognition memory
    and locomotor dysfunction. Its value here is the rescue design rather than the
    phenotype: it separates the CNS consequences into two classes with different
    therapeutic windows. Anxiety and memory deficits were relieved by high-dose
    thyroid hormone given in adulthood, correlating with normalized GABAergic
    inhibitory interneurons in hippocampal CA1, whereas the locomotor dysfunction
    required post-natal treatment and was linked to otherwise delayed cerebellar
    development.
  modeled_mechanisms:
  - target: Impaired Central Nervous System Thyroid Hormone Action
    relationship: RESCUES
    fidelity: MODERATE
    model_scale: ORGANISM
    description: >-
      Thyroid hormone rescues part of the CNS phenotype, and the part it rescues
      depends on when it is given. This is the closest experimental evidence
      bearing on whether levothyroxine started late can help, which is the open
      clinical question for this disorder.
    limitations: >-
      The lesion is reduced ligand affinity, not the dominant-negative corepressor
      retention that causes human RTH-alpha, so a hormone-dose rescue is expected
      to work better here than in a patient whose mutant receptor is
      transcriptionally inert. The rescued readouts are rodent behavioural assays
      (anxiety, recognition memory, locomotion), which map only loosely onto the
      human phenotype of dyspraxia, dysarthria and reduced IQ. Treatment was
      high-dose thyroid hormone in a mouse, not a clinical levothyroxine regimen.
    divergences:
    - divergence_type: PROXY_QUANTITY
      materiality: QUALIFYING
      description: >-
        The measured quantities are murine anxiety, recognition memory and
        locomotor performance. The node's quantity is impaired thyroid hormone
        action in the human central nervous system, manifesting as developmental
        delay, dyspraxia and intellectual disability.
    evidence:
    - reference: PMID:16131613
      reference_title: Anxiety, memory impairment, and locomotor dysfunction caused by a mutant thyroid hormone receptor alpha1 can be ameliorated by T3 treatment.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "The anxiety and memory deficiencies were relieved by treatment with high levels of TH in adulthood, an effect that correlated with a normalization of GABAergic inhibitory interneurons in the hippocampal CA1 region."
      explanation: >-
        The adult-rescuable arm, with its cellular correlate in GABAergic
        interneurons - the same cell population the human epilepsy association is
        attributed to.
    - reference: PMID:16131613
      reference_title: Anxiety, memory impairment, and locomotor dysfunction caused by a mutant thyroid hormone receptor alpha1 can be ameliorated by T3 treatment.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "In contrast, a post-natal TH treatment was necessary and sufficient for ameliorating the adult locomotor dysfunction."
      explanation: >-
        The developmentally fixed arm. Cited alongside the previous item because
        together they make the claim this link exists for: the therapeutic window
        is not one window but several, differing by readout.
  evidence:
  - reference: PMID:16131613
    reference_title: Anxiety, memory impairment, and locomotor dysfunction caused by a mutant thyroid hormone receptor alpha1 can be ameliorated by T3 treatment.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "we introduced a mutation into the mouse TRalpha1 gene that lowers affinity to thyroid hormone (TH) 10-fold"
    explanation: >-
      States the construct, which is what bounds this model's relevance: reduced
      ligand affinity rather than the dominant-negative mechanism of human
      RTH-alpha.
differential_diagnoses:
- name: Allan-Herndon-Dudley syndrome (MCT8 deficiency)
  description: >-
    The closest biochemical mimic, and the one that matters most because the
    lesion is in the opposite part of the pathway: MCT8 is a transporter, so
    hormone cannot reach the cell, whereas in RTH-alpha hormone reaches the cell
    normally and the receptor cannot act on it. Both produce a discordant thyroid
    panel with a non-suppressed TSH and neurodevelopmental impairment.
  disease_term:
    preferred_term: Allan-Herndon-Dudley syndrome
    term:
      id: MONDO:0010354
      label: Allan-Herndon-Dudley syndrome
  distinguishing_features:
  - >-
    AHDS has markedly elevated T3 with an elevated T3/T4 ratio and prominent
    peripheral thyrotoxic features - resting tachycardia, progressive weight
    loss, muscle wasting, failure to thrive. RTH-alpha has only high-normal to
    mildly raised T3, a subnormal T4/T3 ratio, and bradycardia rather than
    tachycardia in the minority with a rate abnormality.
  - >-
    AHDS is X-linked and the neurological picture is far more severe - spastic
    quadriplegia, absent speech, dystonia - whereas RTH-alpha is autosomal
    dominant with mild-to-moderate impairment.
  - >-
    Reverse T3 is low in both, so it does not separate them. Definitive
    separation is by sequencing SLC16A2 versus THRA.
  evidence:
  - reference: PMID:39201272
    reference_title: "Normal Values for the fT3/fT4 Ratio: Centile Charts (0-29 Years) and Their Application for the Differential Diagnosis of Children with Developmental Delay."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "individuals with developmental delay and genetically confirmed thyroid hormone resistance, carrying defects in Monocarboxylate Transporter 8 (MCT8), Thyroid Hormone Receptor alpha (THRα), and Selenocysteine Insertion Sequence-Binding Protein 2 (SECISBP2)"
    explanation: >-
      Groups MCT8, THRA and SECISBP2 defects as the differential set reached
      through the same presenting problem and the same ratio-based screen.
  - reference: PMID:39132310
    reference_title: "Unmet patient needs in monocarboxylate transporter 8 (MCT8) deficiency: a review."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Both RTH- α and MCT8 de ﬁciency may be associated with neurocognitive
      deﬁcits and developmental delay, however, RTH- α is associated with
      bradycardia a nd skeletal anomalies, while MCT8 de ﬁciency is associated
      with tachycardia and failure
    explanation: >-
      Gives the discriminating pair directly - bradycardia and skeletal anomalies
      in RTH-alpha against tachycardia and failure to thrive in MCT8 deficiency -
      which is the first distinguishing feature above. The broken words and
      ligatures are artifacts of the cached full text and are quoted as they
      appear.
  - reference: PMID:39132310
    reference_title: "Unmet patient needs in monocarboxylate transporter 8 (MCT8) deficiency: a review."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The only characteristic MCT8-related thyroid hormone alteration that is
      present within the newborn period is a low reverse T3 (rT3)
    explanation: >-
      Supports the third distinguishing feature: reverse T3 is low in MCT8
      deficiency too, so it cannot be used to separate the two disorders.
- name: Generalized resistance to thyroid hormone (RTH-beta)
  description: >-
    The same class of lesion in the other receptor isoform, and biochemically its
    mirror image. Because TR-beta carries pituitary feedback, a THRB
    dominant-negative variant breaks the feedback loop and produces elevated free
    T4 and free T3 with a non-suppressed TSH - the opposite laboratory picture
    from RTH-alpha, where the loop is intact and TSH is simply normal.
  disease_term:
    preferred_term: generalized resistance to thyroid hormone
    term:
      id: MONDO:0009043
      label: generalized resistance to thyroid hormone
  distinguishing_features:
  - >-
    RTH-beta has raised free T4 and free T3 with a non-suppressed TSH;
    RTH-alpha has low or low-normal free T4, high-normal or high free T3, and a
    normal TSH. The TSH in RTH-beta is inappropriate for the elevated hormone
    levels, whereas in RTH-alpha it is simply normal.
  - >-
    RTH-beta commonly presents with goiter and tachycardia; RTH-alpha is
    nongoitrous and if anything bradycardic.
  - >-
    Separation is by which gene is sequenced - THRB versus THRA.
  evidence:
  - reference: PMID:28527577
    reference_title: Resistance to Thyroid Hormone due to Heterozygous Mutations in Thyroid Hormone Receptor Alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients with mutations in THRB, exhibiting resistance within the hypothalamic-pituitary-thyroid axis with elevated TH and nonsuppressed thyroid-stimulating hormone (TSH) levels, were first described decades ago."
    explanation: >-
      States the RTH-beta biochemical signature - elevated hormone with a
      non-suppressed TSH - against which the RTH-alpha profile is contrasted.
  - reference: PMID:32349464
    reference_title: The Clinical Spectrum of Resistance to Thyroid Hormone Alpha in Children and Adults.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The incidence of RTHβ is reported to be approximately 1/40000 and is characterized by goiter, tachycardia, hyperactivity, failure to thrive and cognitive impairments with high serum TH levels, but normal or mildly elevated TSH"
    explanation: >-
      Supplies the clinical half of the separation - goiter and tachycardia in
      RTH-beta - and incidentally shows RTH-beta is roughly three orders of
      magnitude commoner than RTH-alpha.
- name: Primary congenital hypothyroidism
  description: >-
    The condition RTH-alpha is most often mistaken for clinically and least
    likely to be confused with biochemically, once a thyroid panel is done. The
    clinical picture overlaps substantially - growth retardation, developmental
    delay, constipation, delayed bone age - but congenital hypothyroidism is
    defined by an elevated TSH, which is what newborn screening detects and what
    RTH-alpha lacks.
  disease_term:
    preferred_term: congenital hypothyroidism
    term:
      id: MONDO:0018612
      label: congenital hypothyroidism
  distinguishing_features:
  - >-
    Primary congenital hypothyroidism has an elevated TSH and is detected by
    newborn screening; RTH-alpha has a normal TSH and is not.
  - >-
    In primary congenital hypothyroidism both free T4 and free T3 are low; in
    RTH-alpha free T3 is high-normal or high while free T4 is low-normal, giving
    the subnormal T4/T3 ratio that is absent in hormone deficiency.
  evidence:
  - reference: PMID:39201272
    reference_title: "Normal Values for the fT3/fT4 Ratio: Centile Charts (0-29 Years) and Their Application for the Differential Diagnosis of Children with Developmental Delay."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "children with congenital hypothyroidism and reduced thyroid hormone production are diagnosed on the basis of elevated plasma TSH levels"
    explanation: >-
      States the TSH-based diagnostic basis for congenital hypothyroidism, which
      is the axis on which the two are separated.
discussions:
- discussion_id: rtha_levothyroxine_outcome_benefit
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    Does levothyroxine improve long-term outcomes in RTH-alpha, and does
    starting it in adulthood help at all?
  attaches_to:
  - treatments#Levothyroxine
  rationale: >-
    Everything known about treatment benefit in RTH-alpha comes from case series
    of single-digit size with no control arm and no randomization, in a disorder
    with fewer than fifty published patients. The largest follow-up study
    enrolled seven patients from two families. Within that evidence base the
    short-term biochemical and symptomatic effects are reasonably clear
    (constipation relieved, creatine kinase lowered, anaemia not), but the
    questions that matter clinically are not answered: whether final height,
    adult cognitive outcome or cardiovascular risk differ with treatment, and
    whether initiating thyroxine in an adult diagnosed late does anything. The
    untreated adult series raises the possibility that the window is early
    childhood, since untreated adults had a more pronounced phenotype than
    patients treated from childhood - but that is a between-cohort comparison,
    not evidence of effect. The 2024 European Thyroid Association guideline
    describes the whole family of these disorders as managed on a limited
    evidence base. This will not be resolved by a trial at this prevalence; a
    prospective international registry with a common outcome set is the
    realistic route.

      One experimental result bears on it directly and cuts both ways. In a
      low-T3-affinity TR-alpha1 knock-in mouse, anxiety and recognition-memory
      deficits were rescued by high-dose thyroid hormone given in adulthood, while
      the locomotor deficit required post-natal treatment and was tied to cerebellar
      development. If that separation holds in humans, "does adult treatment help"
      has no single answer - it depends which deficit is asked about, and this
      entry's observation that IQ improved in every treated child except the one
      diagnosed at 9.5 years is consistent with a graded rather than an absolute
      window. The caveat is that the mouse lesion is reduced ligand affinity, not
      dominant-negative corepressor retention, so hormone dose should work better
      there than in a patient whose mutant receptor is transcriptionally inert.
  evidence:
  - reference: PMID:37469961
    reference_title: Clinical and Biochemical Characteristics of Untreated Adult Patients With Resistance to Thyroid Hormone Alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "However, it is not clear if treatment has beneficial effects if started in adulthood."
    explanation: States the adult-initiation question as explicitly open.
  - reference: PMID:26303090
    reference_title: Resistance to thyroid hormone due to defective thyroid receptor alpha.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The genetic and phenotypic heterogeneity of RTHα and its optimal management remain to be elucidated."
    explanation: An independent statement that optimal management is unresolved.
  - reference: PMID:38963712
    reference_title: 2024 European Thyroid Association Guidelines on diagnosis and management of genetic disorders of thyroid hormone transport, metabolism and action.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "managing these rare disorders with a limited evidence base"
    explanation: >-
      The current guideline's own characterization of the evidence base it is
      built on, which is the honest ceiling on any treatment claim in this entry.
  - reference: PMID:16131613
    reference_title: Anxiety, memory impairment, and locomotor dysfunction caused by a mutant thyroid hormone receptor alpha1 can be ameliorated by T3 treatment.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In contrast, a post-natal TH treatment was necessary and sufficient for ameliorating the adult locomotor dysfunction."
    explanation: >-
      Model-system evidence that some consequences have a developmental window that
      closes, which is what makes the adult-initiation question substantive rather
      than merely unstudied.
- discussion_id: rtha_ncor1_targeting_translational_validity
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  prompt: >-
    The mouse work shows that preventing NCOR1 recruitment by mutant TR-alpha1
    reverses growth, bone and erythroid phenotypes. Is the TR-alpha1-NCOR1
    interaction a tractable target in human RTH-alpha, or is the rescue an
    artifact of a genetic manipulation with no pharmacological counterpart?
  attaches_to:
  - pathophysiology#Persistent Corepressor Occupancy at Thyroid Hormone Response Elements
  rationale: >-
    The evidence here is not absent - it is strong, and it is in a mouse. The
    Thra1PV/+ by Ncor1-delta-ID cross is the cleanest mechanistic experiment in
    the field, and it establishes corepressor recruitment as causal rather than
    correlated. But the intervention is a germline-engineered corepressor that
    cannot be recruited, present from conception, which is not a drug and has no
    obvious human equivalent. Two things make the translational question live
    rather than academic. First, the rescue is explicitly partial even in the
    mouse. Second, the one finding in this disorder that directly addresses
    reversibility in the other direction - the cardiac work - found that several
    heart-rate genes are irreversibly down-regulated and that restoring them
    required raising T3 in utero, which implies some consequences are
    developmentally fixed before any postnatal intervention could reach them. A
    structure-guided ligand analogue, ES08, that dissociates corepressor from
    mutant TR-alpha more efficiently than T3 is the first candidate with a
    plausible route to patients, but its in vivo evidence is in zebrafish and its
    human evidence is in patient-derived cells, not in patients. Recorded as
    HUMAN_MODEL_MISMATCH rather than KNOWLEDGE_GAP because the model evidence
    exists and is good; what is unknown is whether it transfers.
  evidence:
  - reference: PMID:23610395
    reference_title: Nuclear receptor corepressor (NCOR1) regulates in vivo actions of a mutated thyroid hormone receptor α.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Therefore, therapies aimed at the TRα1-NCOR1 interaction or its downstream actions could be tested as potential targets in treating TRα1 mutant-mediated hypothyroidism in patients."
    explanation: >-
      The authors propose the interaction as a human target, i.e. they themselves
      frame this as an untested translational step.
  - reference: PMID:34871063
    reference_title: Structure-Guided Approach to Relieving Transcriptional Repression in Resistance to Thyroid Hormone α.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Our observations provide proof of principle for developing synthetic ligands that can relieve transcriptional repression by the mutant TRα-corepressor complex for treatment of RTHα."
    explanation: >-
      Describes the corepressor-dissociating ligand as proof of principle, which
      is the current ceiling of the translational claim.
  - reference: PMID:37286550
    reference_title: Resistance to thyroid hormone induced tachycardia in RTHα syndrome.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Exposure of TRα1 mutant male mice to higher maternal T3 concentrations in utero, restores altered expression and DNA methylation of ion channels, including Ryr2."
    explanation: >-
      Shows that correcting at least one set of consequences required an in utero
      intervention, which bears directly on whether any therapy given after birth
      could reach them.
references:
- reference: PMID:38963712
  title: 2024 European Thyroid Association Guidelines on diagnosis and management of genetic disorders of thyroid hormone transport, metabolism and action.
notes: >-
  MONDO identity. This entry anchors on MONDO:0013757 ("congenital nongoitrous
  hypothyroidism 6") and asserts skos:exactMatch to MONDO:0034216 ("resistance to
  thyroid hormone due to a mutation in thyroid hormone receptor alpha"), because
  the two are an unmerged duplicate pair denoting the same THRA disease rather
  than two concepts. The reasoning, checked against OLS on 2026-09-10, is set out
  in full in mappings.mondo_mappings; the decisive observation is that Orphanet's
  own ORDO record for ORPHA:566231 - the source of MONDO:0034216 - itself
  cross-references OMIM:614450, which is the source of MONDO:0013757. Both MONDO
  terms are leaves, neither is an ancestor of the other, and they hang from
  different parents (MONDO:0013757 under "hypothyroidism, congenital,
  nongoitrous" and "peripheral resistance to thyroid hormones"; MONDO:0034216
  under "thyroid hormone resistance syndrome"), which is what makes the
  duplication easy to miss. Asserting exactMatch rather than closeMatch is
  deliberate: it retires both identifiers from the curation queue, which is the
  correct outcome if they are one disease, and a weaker predicate would leave
  MONDO:0034216 open for re-nomination as a separate entry. Worth reporting
  upstream to MONDO as a merge candidate; this entry does not assume that has
  happened.

  Entry name. Named "Resistance to Thyroid Hormone Alpha" rather than the stub's
  proposed "Congenital_Nongoitrous_Hypothyroidism_6". Three reasons. The
  clinically preferred name is the one the literature uses - every cited source
  from 2013 onwards calls the disorder RTH-alpha, and the CHNG6 title survives
  only as an OMIM artifact of the disorder having been first recognized as a
  hypothyroidism-like presentation. The ontology work above concluded that
  MONDO:0013757 is not a narrower CHNG6-specific concept but the same disease as
  MONDO:0034216, whose own label is the resistance name, so nothing argues for
  the narrower title. And it parallels the existing sibling entry
  Generalized_Resistance_to_Thyroid_Hormone (RTH-beta, MONDO:0009043), which
  matters because the two entries are each other's primary differential. The
  CHNG6 label and its synonyms are retained in synonyms: so the concept remains
  findable under either name.

  No conforms_to, deliberately. Two candidate modules were examined and both
  rejected. kb/modules/hypothyroidism_thyroid_hormone_deficiency.yaml is the
  mechanistic inverse of this disorder, not a variant of it: its chain begins
  "Impaired Thyroid Hormone Synthesis" then "Thyroid Hormone Insufficiency",
  whereas in RTH-alpha hormone synthesis and circulating hormone are normal and
  the lesion is in the receptor. Conforming a single middle node ("Reduced
  Thyroid Hormone Action at Peripheral Sites") while its declared upstream node
  is absent would assert a hormone deficiency that this disorder does not have.
  This is the same judgement, for the same reason, that
  Generalized_Resistance_to_Thyroid_Hormone recorded for RTH-beta.
  kb/modules/defective_skeletal_mineralization.yaml was also checked because of
  the skeletal phenotype and rejected: its rate-limiting step is failure to
  deposit hydroxyapatite at the mineralization front with a calciopenic,
  phosphopenic or inhibitor-excess trigger, none of which applies here - the
  RTH-alpha skeletal lesion is delayed chondrocyte maturation and ossification
  with normal mineral substrate. A receptor-resistance module covering RTH-alpha,
  RTH-beta, MCT8 deficiency and SECISBP2 deficiency would be a genuine candidate
  for future work, since all four share the shape "hormone present, signal not
  received"; it does not exist and was not created in this pass.

  Deep research. The assigned provider (falcon/Edison) returned HTTP 402 Payment
  Required - the account is out of credits - on two consecutive attempts, and the
  openscientist fallback timed out after 3600 s. A third run with the claude_code
  provider under --fallback succeeded and is committed as
  research/Resistance_to_Thyroid_Hormone_Alpha-deep-research-claude_code.md; the
  provider substitution is recorded in that report's own frontmatter rather than
  only in prose. The first draft of this entry predates the report and was built
  from primary literature located by direct PubMed searches; the report was then
  read as a source of leads and each lead checked against the primary source
  before being curated. just preflight-dr passed, confirming the report is about
  THRA (34 mentions) and that its OMIM identifier, 614450, matches the one MONDO
  gives for MONDO:0013757 - independent corroboration of the mapping decision
  above.

  What the report added, after checking: the wormian bones, cranial hyperostosis,
  skin tags, delayed speech and language development, gait ataxia, seizure and
  hepatic steatosis phenotypes; sourced frequencies for short stature (60%),
  macrocephaly (70%) and delayed tooth eruption (44%); the colonic-manometry
  finding that raised the gastrointestinal node from PROVISIONAL to ESTABLISHED;
  human erythroid-progenitor evidence (PMID:28911146), which was the entry's most
  substantive gap because the erythroid node previously rested on mouse data
  alone; the low-T3-affinity TR-alpha1 rescue mouse (PMID:16131613), whose split
  adult-versus-postnatal therapeutic window materially sharpens the levothyroxine
  knowledge gap; and a 2026 kindred (PMID:42301959) documenting age-related
  attenuation, which is the basis of the progression section.

  What the report got wrong, recorded so it is not re-imported. Three ontology
  bindings it offered are wrong, all three flagged by the report's own Term
  Validation section and each confirmed by direct lookup against ols:hp or
  ols:go: HP:0010701 offered for "Skin tags" is Abnormal circulating
  immunoglobulin concentration (the correct term, HP:0010609, was found
  independently and is what this entry binds); HP:0001923 offered for "Normocytic
  anemia" is Reticulocytosis; and GO:0004887 offered for "thyroid hormone receptor
  activity" is obsolete, replaced by GO:0004879 - which this entry already bound
  from its own lookup. It also offered UBERON:0001968 for "skeletal system", which
  is semen, and HP:0008977 for "Decreased basal metabolic rate", which does not
  resolve at all. None of these was bound. Two substantive claims also failed
  checking. The report described "increased bone mineral density" as characteristic
  in adults; the review it cites reports bone mineral density as normal in the
  three adults in whom it was measured, and that contradiction is curated as a
  REFUTE evidence item on the Cranial hyperostosis phenotype rather than dropped.
  And it cited PMID:28856816 as identifying THRA variants in autism cohorts,
  offering Autistic behavior as an RTH-alpha phenotype; reading that paper shows it
  reports novel single-nucleotide polymorphisms of uncertain significance in the
  ligand-binding domains of THRA and THRB in 30 ASD subjects, not pathogenic
  RTH-alpha variants in RTH-alpha patients, so treating it as evidence for an
  autism phenotype of this disease would be a category error. No autism phenotype
  was curated and PMID:28856816 is not cited. Finally, a creatine kinase figure it
  gave ("73%, 8/11 untreated children, range 218-981 U/L") could not be located in
  the source it was attributed to and was not used.

  No GeneReviews chapter exists for RTH-alpha. A PubMed search for
  "resistance to thyroid hormone alpha GeneReviews[All Fields]" returns a single
  hit which is the GNAS chapter, matched on the book series name rather than the
  subject; "THRA GeneReviews[All Fields]" returns nothing. This is consistent
  with what Generalized_Resistance_to_Thyroid_Hormone records for RTH-beta,
  RTH-alpha and SECISBP2 deficiency. The baseline clinical reference used instead
  is the 2024 European Thyroid Association guideline (PMID:38963712, listed under
  references), whose cached record is abstract-only, plus the two clinical-spectrum
  reviews PMID:32349464 and PMID:26303090.

  Boundary against the adjacent entries. The three curated disorders of impaired
  thyroid hormone sensitivity are distinguished by where in the pathway the
  lesion sits, and the entry is written to keep those distinct rather than
  duplicating either neighbour's pathograph. Allan-Herndon-Dudley_Syndrome
  (SLC16A2/MCT8, MONDO:0010354) is a transport defect - hormone cannot enter the
  cell. SECISBP2_Deficiency is a metabolism defect. This entry is a receptor
  defect - hormone enters normally and cannot be acted upon - and
  Generalized_Resistance_to_Thyroid_Hormone is the receptor defect in the other
  isoform, with the opposite biochemical consequence because TR-beta is the
  isoform carrying pituitary feedback. All three are cross-referenced in
  differential_diagnoses with the features that separate them. Note that the
  existing Allan-Herndon-Dudley_Syndrome entry already names this disorder in its
  differential_diagnoses using MONDO:0034216; that reference remains correct, as
  it is an ontology term rather than an entry reference.

  Deliberately omitted, with reasons. (1) No cell_types on the "Impaired
  Gastrointestinal Motility" node - constipation and an intestinal site of
  TR-alpha action are both well documented, but nothing located identifies the
  responsible cell type in human disease, and that node is marked
  mechanism_confidence: PROVISIONAL for the same reason. (2) No reference
  interval bounds for reverse T3, creatine kinase, haemoglobin or MCV: the cited
  sources report medians or ratios to a local upper limit rather than intervals,
  and paediatric intervals for these analytes are strongly age-dependent. The
  analyte LOINC codes are bound without bounds so the measurements remain
  machine-queryable. All eight LOINC codes used here were resolved against the
  NLM Clinical Table Search Service on 2026-09-10; LOINC is not configured in
  conf/oak_config.yaml, so none of them is covered by just validate-terms and
  they should be treated as verified-by-hand rather than gate-checked. (3) No
  biomarker_term on the free T4 to free T3 ratio entry: searches of ols:ncit
  found no term for this ratio (NCIT:C181446 is the thyrotropin-to-free-thyroxine
  ratio), and LOINC:57899-7 is the T3-to-reverse-T3 ratio, not this one. (4) TSH
  is bound to the analyte term NCIT:C2280 rather than a measurement term because
  NCIT has no "Thyroid Stimulating Hormone Measurement" analogous to NCIT:C74786
  and NCIT:C74787. (5) No ORPHA evidence, despite ORPHA:566231 carrying both a
  good definition and the epidemiology figures quoted in the prevalence notes:
  the Orphadata bulk XML is not present in this checkout and fetching it was out
  of scope, so no ORPHA snippet could be exact-quote verified. (6) No
  clinical_trials and no datasets: no interventional trial and no disease-specific
  dataset accession was located for RTH-alpha, and inventing either is worse than
  their absence. (7) No has_subtypes: the genotype-phenotype correlation is real
  and well documented (truncating and C-terminal variants more severe than
  N-terminal missense variants, with correspondingly different levothyroxine
  response) but it is a severity gradient across a continuum of variants, not a
  set of named subtypes, and no source partitions it. It is recorded in the
  genetic section and in the treatment description instead. (8) Skin tags,
  decreased metabolic rate and pericardial effusion appear in the Orphanet
  description or in single cohorts but were not curated as phenotypes, because
  the evidence located for each was a single series and in the case of skin tags
  and metabolic rate only the uncited Orphanet text. (9) No computational_models
  section: no kinetic, network or structural model of TR-alpha1-corepressor
  dynamics in RTH-alpha was located. One experimental_models entry is present (the
  patient-derived primary erythroid progenitor culture); patient-derived peripheral
  blood mononuclear cell and fibroblast transactivation assays are cited inside
  evidence items but are single-experiment readouts rather than standing models.
  (10) No autism phenotype, despite a deep-research lead proposing one - see the
  rejected-leads paragraph above. (11) The skeletal node's downstream list now
  includes wormian bones and cranial hyperostosis as consequences of delayed
  cranial ossification, but no separate node is created for the cranial vault: the
  sources treat the calvarial findings as part of the same skeletal dysplasia, and
  splitting them would assert a distinct mechanism nothing supports.

📚

References & Deep Research

References

1

PMID:38963712

2024 European Thyroid Association Guidelines on diagnosis and management of genetic disorders of thyroid hormone transport, metabolism and action.

No top-level findings curated for this source.

Deep Research

1

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Evaluations and curation notes (3)

Record notes

MONDO identity. This entry anchors on MONDO:0013757 ("congenital nongoitrous hypothyroidism 6") and asserts skos:exactMatch to MONDO:0034216 ("resistance to thyroid hormone due to a mutation in thyroid hormone receptor alpha"), because the two are an unmerged duplicate pair denoting the same THRA disease rather than two concepts. The reasoning, checked against OLS on 2026-09-10, is set out in full in mappings.mondo_mappings; the decisive observation is that Orphanet's own ORDO record for ORPHA:566231 - the source of MONDO:0034216 - itself cross-references OMIM:614450, which is the source of MONDO:0013757. Both MONDO terms are leaves, neither is an ancestor of the other, and they hang from different parents (MONDO:0013757 under "hypothyroidism, congenital, nongoitrous" and "peripheral resistance to thyroid hormones"; MONDO:0034216 under "thyroid hormone resistance syndrome"), which is what makes the duplication easy to miss. Asserting exactMatch rather than closeMatch is deliberate: it retires both identifiers from the curation queue, which is the correct outcome if they are one disease, and a weaker predicate would leave MONDO:0034216 open for re-nomination as a separate entry. Worth reporting upstream to MONDO as a merge candidate; this entry does not assume that has happened. Entry name. Named "Resistance to Thyroid Hormone Alpha" rather than the stub's proposed "Congenital_Nongoitrous_Hypothyroidism_6". Three reasons. The clinically preferred name is the one the literature uses - every cited source from 2013 onwards calls the disorder RTH-alpha, and the CHNG6 title survives only as an OMIM artifact of the disorder having been first recognized as a hypothyroidism-like presentation. The ontology work above concluded that MONDO:0013757 is not a narrower CHNG6-specific concept but the same disease as MONDO:0034216, whose own label is the resistance name, so nothing argues for the narrower title. And it parallels the existing sibling entry Generalized_Resistance_to_Thyroid_Hormone (RTH-beta, MONDO:0009043), which matters because the two entries are each other's primary differential. The CHNG6 label and its synonyms are retained in synonyms: so the concept remains findable under either name. No conforms_to, deliberately. Two candidate modules were examined and both rejected. kb/modules/hypothyroidism_thyroid_hormone_deficiency.yaml is the mechanistic inverse of this disorder, not a variant of it: its chain begins "Impaired Thyroid Hormone Synthesis" then "Thyroid Hormone Insufficiency", whereas in RTH-alpha hormone synthesis and circulating hormone are normal and the lesion is in the receptor. Conforming a single middle node ("Reduced Thyroid Hormone Action at Peripheral Sites") while its declared upstream node is absent would assert a hormone deficiency that this disorder does not have. This is the same judgement, for the same reason, that Generalized_Resistance_to_Thyroid_Hormone recorded for RTH-beta. kb/modules/defective_skeletal_mineralization.yaml was also checked because of the skeletal phenotype and rejected: its rate-limiting step is failure to deposit hydroxyapatite at the mineralization front with a calciopenic, phosphopenic or inhibitor-excess trigger, none of which applies here - the RTH-alpha skeletal lesion is delayed chondrocyte maturation and ossification with normal mineral substrate. A receptor-resistance module covering RTH-alpha, RTH-beta, MCT8 deficiency and SECISBP2 deficiency would be a genuine candidate for future work, since all four share the shape "hormone present, signal not received"; it does not exist and was not created in this pass. Deep research. The assigned provider (falcon/Edison) returned HTTP 402 Payment Required - the account is out of credits - on two consecutive attempts, and the openscientist fallback timed out after 3600 s. A third run with the claude_code provider under --fallback succeeded and is committed as research/Resistance_to_Thyroid_Hormone_Alpha-deep-research-claude_code.md; the provider substitution is recorded in that report's own frontmatter rather than only in prose. The first draft of this entry predates the report and was built from primary literature located by direct PubMed searches; the report was then read as a source of leads and each lead checked against the primary source before being curated. just preflight-dr passed, confirming the report is about THRA (34 mentions) and that its OMIM identifier, 614450, matches the one MONDO gives for MONDO:0013757 - independent corroboration of the mapping decision above. What the report added, after checking: the wormian bones, cranial hyperostosis, skin tags, delayed speech and language development, gait ataxia, seizure and hepatic steatosis phenotypes; sourced frequencies for short stature (60%), macrocephaly (70%) and delayed tooth eruption (44%); the colonic-manometry finding that raised the gastrointestinal node from PROVISIONAL to ESTABLISHED; human erythroid-progenitor evidence (PMID:28911146), which was the entry's most substantive gap because the erythroid node previously rested on mouse data alone; the low-T3-affinity TR-alpha1 rescue mouse (PMID:16131613), whose split adult-versus-postnatal therapeutic window materially sharpens the levothyroxine knowledge gap; and a 2026 kindred (PMID:42301959) documenting age-related attenuation, which is the basis of the progression section. What the report got wrong, recorded so it is not re-imported. Three ontology bindings it offered are wrong, all three flagged by the report's own Term Validation section and each confirmed by direct lookup against ols:hp or ols:go: HP:0010701 offered for "Skin tags" is Abnormal circulating immunoglobulin concentration (the correct term, HP:0010609, was found independently and is what this entry binds); HP:0001923 offered for "Normocytic anemia" is Reticulocytosis; and GO:0004887 offered for "thyroid hormone receptor activity" is obsolete, replaced by GO:0004879 - which this entry already bound from its own lookup. It also offered UBERON:0001968 for "skeletal system", which is semen, and HP:0008977 for "Decreased basal metabolic rate", which does not resolve at all. None of these was bound. Two substantive claims also failed checking. The report described "increased bone mineral density" as characteristic in adults; the review it cites reports bone mineral density as normal in the three adults in whom it was measured, and that contradiction is curated as a REFUTE evidence item on the Cranial hyperostosis phenotype rather than dropped. And it cited PMID:28856816 as identifying THRA variants in autism cohorts, offering Autistic behavior as an RTH-alpha phenotype; reading that paper shows it reports novel single-nucleotide polymorphisms of uncertain significance in the ligand-binding domains of THRA and THRB in 30 ASD subjects, not pathogenic RTH-alpha variants in RTH-alpha patients, so treating it as evidence for an autism phenotype of this disease would be a category error. No autism phenotype was curated and PMID:28856816 is not cited. Finally, a creatine kinase figure it gave ("73%, 8/11 untreated children, range 218-981 U/L") could not be located in the source it was attributed to and was not used. No GeneReviews chapter exists for RTH-alpha. A PubMed search for "resistance to thyroid hormone alpha GeneReviews[All Fields]" returns a single hit which is the GNAS chapter, matched on the book series name rather than the subject; "THRA GeneReviews[All Fields]" returns nothing. This is consistent with what Generalized_Resistance_to_Thyroid_Hormone records for RTH-beta, RTH-alpha and SECISBP2 deficiency. The baseline clinical reference used instead is the 2024 European Thyroid Association guideline (PMID:38963712, listed under references), whose cached record is abstract-only, plus the two clinical-spectrum reviews PMID:32349464 and PMID:26303090. Boundary against the adjacent entries. The three curated disorders of impaired thyroid hormone sensitivity are distinguished by where in the pathway the lesion sits, and the entry is written to keep those distinct rather than duplicating either neighbour's pathograph. Allan-Herndon-Dudley_Syndrome (SLC16A2/MCT8, MONDO:0010354) is a transport defect - hormone cannot enter the cell. SECISBP2_Deficiency is a metabolism defect. This entry is a receptor defect - hormone enters normally and cannot be acted upon - and Generalized_Resistance_to_Thyroid_Hormone is the receptor defect in the other isoform, with the opposite biochemical consequence because TR-beta is the isoform carrying pituitary feedback. All three are cross-referenced in differential_diagnoses with the features that separate them. Note that the existing Allan-Herndon-Dudley_Syndrome entry already names this disorder in its differential_diagnoses using MONDO:0034216; that reference remains correct, as it is an ontology term rather than an entry reference. Deliberately omitted, with reasons. (1) No cell_types on the "Impaired Gastrointestinal Motility" node - constipation and an intestinal site of TR-alpha action are both well documented, but nothing located identifies the responsible cell type in human disease, and that node is marked mechanism_confidence: PROVISIONAL for the same reason. (2) No reference interval bounds for reverse T3, creatine kinase, haemoglobin or MCV: the cited sources report medians or ratios to a local upper limit rather than intervals, and paediatric intervals for these analytes are strongly age-dependent. The analyte LOINC codes are bound without bounds so the measurements remain machine-queryable. All eight LOINC codes used here were resolved against the NLM Clinical Table Search Service on 2026-09-10; LOINC is not configured in conf/oak_config.yaml, so none of them is covered by just validate-terms and they should be treated as verified-by-hand rather than gate-checked. (3) No biomarker_term on the free T4 to free T3 ratio entry: searches of ols:ncit found no term for this ratio (NCIT:C181446 is the thyrotropin-to-free-thyroxine ratio), and LOINC:57899-7 is the T3-to-reverse-T3 ratio, not this one. (4) TSH is bound to the analyte term NCIT:C2280 rather than a measurement term because NCIT has no "Thyroid Stimulating Hormone Measurement" analogous to NCIT:C74786 and NCIT:C74787. (5) No ORPHA evidence, despite ORPHA:566231 carrying both a good definition and the epidemiology figures quoted in the prevalence notes: the Orphadata bulk XML is not present in this checkout and fetching it was out of scope, so no ORPHA snippet could be exact-quote verified. (6) No clinical_trials and no datasets: no interventional trial and no disease-specific dataset accession was located for RTH-alpha, and inventing either is worse than their absence. (7) No has_subtypes: the genotype-phenotype correlation is real and well documented (truncating and C-terminal variants more severe than N-terminal missense variants, with correspondingly different levothyroxine response) but it is a severity gradient across a continuum of variants, not a set of named subtypes, and no source partitions it. It is recorded in the genetic section and in the treatment description instead. (8) Skin tags, decreased metabolic rate and pericardial effusion appear in the Orphanet description or in single cohorts but were not curated as phenotypes, because the evidence located for each was a single series and in the case of skin tags and metabolic rate only the uncited Orphanet text. (9) No computational_models section: no kinetic, network or structural model of TR-alpha1-corepressor dynamics in RTH-alpha was located. One experimental_models entry is present (the patient-derived primary erythroid progenitor culture); patient-derived peripheral blood mononuclear cell and fibroblast transactivation assays are cited inside evidence items but are single-experiment readouts rather than standing models. (10) No autism phenotype, despite a deep-research lead proposing one - see the rejected-leads paragraph above. (11) The skeletal node's downstream list now includes wormian bones and cranial hyperostosis as consequences of delayed cranial ossification, but no separate node is created for the cranial vault: the sources treat the calvarial findings as part of the same skeletal dysplasia, and splitting them would assert a distinct mechanism nothing supports.

Integrate claude_code deep-research leads into Resistance to Thyroid Hormone Alpha · 2026-09-10T18:52:29Z · View source

Second curation round for Resistance_to_Thyroid_Hormone_Alpha: obtaining a deep-research report and integrating what survived checking. The first round's record for this entry states that no report existed; that is now superseded by the report committed with this round, and that earlier record is left unedited because it describes its session accurately. DEEP RESEARCH, RESOLVED. The assigned provider falcon (Edison) returned HTTP 402 Payment Required twice ("the account is out of credits"), and the --fallback run's OpenScientist job (d5700215-0d24-42bf-846f-91d50b3902eb) timed out after 3600 s and was cancelled. A third run used the sanctioned fallback mechanism with the claude_code provider: `just dr_fallback='--fallback' research-disorder claude_code Resistance_to_Thyroid_Hormone_Alpha`. It completed in 337.6 s and produced research/Resistance_to_Thyroid_Hormone_Alpha-deep-research-claude_code.md plus its .citations.md sidecar; no _artifacts/ directory was produced. The report's own frontmatter carries the provenance (provider claude_code; models claude-haiku-4-5-20251001 and claude-sonnet-5; 13 web searches; 23 turns; citation_count 25), so the provider substitution lives in the artifact rather than in prose. No provider was substituted by hand at any point. REPORT VALIDATION READ BEFORE USE. reference_validation: 20/20 references resolved, confabulation_rate 0.0, 18/20 on topic. term_validation: needs_review true - 48 terms checked, 44 resolved, 1 unresolved (HP:0008977), 1 obsolete (GO:0004887, replaced by GO:0004879), 6 mislabelled. just preflight-dr PASSED: THRA mentioned 34 times, and the report's OMIM identifier 614450 matches the OMIM that MONDO gives for MONDO:0013757 - independent third-source corroboration of this entry's skos:exactMatch decision between MONDO:0013757 and MONDO:0034216. LEADS ACCEPTED, each checked against the primary source before curating. Seven new phenotypes, all CURIEs resolved by direct lookup: Wormian bones (HP:0002645, 32%), Cranial hyperostosis (HP:0004437), Skin tags (HP:0010609, 21%), Delayed speech and language development (HP:0000750), Gait ataxia (HP:0002066), Seizure (HP:0001250), Hepatic steatosis (HP:0001397). Sourced frequencies added to three existing phenotypes: short stature 60% (12/20 children), macrocephaly 70% (23/33), delayed tooth eruption 44% (8/18). The Impaired Gastrointestinal Motility node was raised from mechanism_confidence: PROVISIONAL to ESTABLISHED, because the report led to a colonic-manometry finding of decreased peristalsis in RTH-alpha patients - a measured human observation, where the first round had only inferred reduced motility from constipation. Human evidence was added to the erythroid node from PMID:28911146 (primary erythroid progenitors from 11 genotyped RTH-alpha patients), which closes the most substantive gap in the first round: that node previously rested on mouse data alone, which CLAUDE.md forbids as the sole support for a human phenotype. That paper also supports a new experimental_models entry (PRIMARY_CELL_CULTURE, two readouts, PARTIALLY_RECAPITULATES with the reason stated: the defect appears only in spontaneous differentiation, and induced differentiation and T3 response were normal). A fourth animal model was added, the low-T3-affinity TR-alpha1 knock-in mouse (PMID:16131613), with relationship RESCUES, because it splits the CNS phenotype by therapeutic window - anxiety and recognition memory rescued by thyroid hormone in adulthood, locomotor dysfunction requiring post-natal treatment. That result materially sharpens the rtha_levothyroxine_outcome_benefit discussion, which now carries it. A new progression section (infancy/early childhood, adulthood) records age-related attenuation of both the clinical picture and the biochemistry, from the 2021 review and a 2026 kindred (PMID:42301959). Four new references were fetched and are cited: PMID:28911146, PMID:16131613, PMID:42301959, and PMID:39132310 (added this round to source the MCT8 differential-diagnosis claims, which were uncited in round one). LEADS REJECTED, recorded in the entry's notes: so they are not re-imported. Three wrong ontology bindings the report offered, each flagged by its own Term Validation and each confirmed wrong by direct lookup: HP:0010701 offered for "Skin tags" is Abnormal circulating immunoglobulin concentration (correct term HP:0010609 found independently); HP:0001923 offered for "Normocytic anemia" is Reticulocytosis; GO:0004887 offered for "thyroid hormone receptor activity" is obsolete, replaced by GO:0004879, which this entry already bound from its own lookup. Also not bound: UBERON:0001968 offered for "skeletal system" (it is semen) and HP:0008977 for "Decreased basal metabolic rate" (does not resolve). Two substantive claims failed checking. The report called increased bone mineral density characteristic in adults; the review it cites reports bone mineral density as NORMAL in the three adults measured, and that contradiction is curated as a supports: REFUTE evidence item on the Cranial hyperostosis phenotype rather than dropped. And it cited PMID:28856816 as evidence for an autism phenotype; that paper reports novel SNPs of uncertain significance in the THRA and THRB ligand-binding domains in 30 ASD subjects, not pathogenic RTH-alpha variants in RTH-alpha patients, so using it would be a category error - no autism phenotype was curated and the PMID is not cited. A creatine kinase figure it gave (73%, 8/11 untreated children, 218-981 U/L) could not be located in the source it was attributed to and was not used. VALIDATION RUN THIS ROUND, with results. just validate - passed. just validate-terms - passed. just count-verified-snippets - 126/126 verified (up from 101). just validate-disorders - passed, 126/126. just check-duplicate-keys, check-entity-refs, check-causal-targets, check-qualifier-terms, check-enum-values - all passed. Whole-KB: check-folded-hyphens, check-snippet-length, check-title-snippets, check-snippet-grading, check-reference-titles - all passed. just normalize-cache and just check-term-cache-integrity - passed, and this round added no new cache rows because every new HP CURIE was already cached by other entries. just compliance - 84.4% global, 84.6% weighted (up from 84.0%). No baseline file was modified. All 24 reference_title values were re-checked character-for-character against their references_cache/ frontmatter; all matched. New downstream edges were added so the new phenotypes are reachable in the pathograph: wormian bones, cranial hyperostosis and coarse facial features from Impaired Skeletal Maturation, and delayed speech, gait ataxia and seizure from Impaired Central Nervous System Thyroid Hormone Action (the last as INDIRECT_KNOWN_INTERMEDIATES, via GABAergic interneuron development). Skin tags and hepatic steatosis are deliberately left unconnected, like hypercholesterolemia, because the liver is TR-beta territory and nothing located explains the skin tags at all; this is stated in the entry.

Create: Resistance to Thyroid Hormone Alpha (THRA, MONDO:0013757) · 2026-09-10T17:37:13Z · View source

De-novo creation of kb/disorders/Resistance_to_Thyroid_Hormone_Alpha.yaml, the THRA receptor disease (resistance to thyroid hormone alpha, RTH-alpha), from the stub stubs/Congenital_Nongoitrous_Hypothyroidism_6.yaml, which this change deletes. Claim issue #11606. LUMP/SPLIT AND ONTOLOGY DECISION. The stub was keyed on MONDO:0013757 ("congenital nongoitrous hypothyroidism 6"), while the existing RTH-beta entry Generalized_Resistance_to_Thyroid_Hormone recorded RTH-alpha as MONDO:0034216 and noted it was not yet curated. Checked both terms directly against OLS (ols:mondo) and Orphanet ORDO (ols:ordo) on 2026-09-10 rather than building a local MONDO database. Finding: the two MONDO terms are an unmerged duplicate pair for one disease. MONDO:0013757 is the OMIM-derived term (defined as "Any hypothyroidism, congenital, nongoitrous in which the cause of the disease is a mutation in the THRA gene", xref OMIM:614450, DOID:0070128); MONDO:0034216 is the Orphanet-derived term (no logical definition, xref Orphanet:566231); and Orphanet's own ORDO record for ORPHA:566231 cross-references BOTH MONDO:0034216 and OMIM:614450. Neither MONDO term asserts a has-exact-match to the other, neither is an ancestor of the other, and they sit under different parents, which is why the duplication is easy to miss. The entry therefore anchors on the stub's MONDO:0013757 and records MONDO:0034216 in mappings.mondo_mappings with mapping_predicate: skos:exactMatch, which is the predicate that retires the mapped concept from the curation queue - the correct consequence if the two are one disease. The full reasoning is in the entry's notes: and in the mapping's own notes:. This should be reported upstream to MONDO as a merge candidate; that was NOT done in this session. NAMING DECISION. Named "Resistance to Thyroid Hormone Alpha" rather than the stub's proposed Congenital_Nongoitrous_Hypothyroidism_6, for three reasons recorded in notes:: the clinically preferred name is what every cited source from 2013 onward uses; the ontology finding above means MONDO:0013757 is not a narrower CHNG6-specific concept, so nothing argues for the narrower title; and it parallels the sibling entry Generalized_Resistance_to_Thyroid_Hormone, with which this entry is mutually differential. The filename uses lowercase "to" to match that sibling exactly. CHNG6 and its synonyms are retained in synonyms:. DEEP RESEARCH. The assigned provider, falcon (Edison), returned HTTP 402 Payment Required ("the account is out of credits") on two consecutive attempts. The second attempt was run with --fallback per repository procedure (just dr_fallback='--fallback' research-disorder falcon ...), so the provider substitution is recorded in the report's own frontmatter rather than only in prose; it fell back to openscientist. That fallback also failed: the OpenScientist job (id d5700215-0d24-42bf-846f-91d50b3902eb) timed out after 3600 s and was cancelled server-side. The fallback chain then stopped, because the provider raised a ValueError which the runner reports as unable to carry the attempt trail, so no further candidate provider was tried. NO DEEP-RESEARCH REPORT EXISTS for this entry - research/Resistance_to_Thyroid_Hormone_Alpha-deep-research-*.md was never written, and nothing from a report is committed with this change. The repository procedure was followed (assigned provider attempted, then one re-run with --fallback) and is exhausted; no provider was substituted by hand. This is a real gap in the curation provenance for this entry and is reported as one rather than worked around. The entry as curated here was built from primary literature located by direct PubMed E-utilities searches, not from a deep-research report. Note that two PMIDs recalled from memory during that search (for the 2012 NEJM index reports) were both wrong - they resolved to unrelated papers on deep-brain stimulation and gonococcal infection - which is the documented reason every identifier here was read from a lookup in the same step it was written. GENEREVIEWS BASELINE. No GeneReviews chapter exists for RTH-alpha. A PubMed search for "resistance to thyroid hormone alpha GeneReviews[All Fields]" returned one hit, PMID:29072892, which is the GNAS chapter matched on the book series name; "THRA GeneReviews[All Fields]" returned nothing. This agrees with what Generalized_Resistance_to_Thyroid_Hormone records. The 2024 European Thyroid Association guideline (PMID:38963712) was used as the baseline reference instead and is listed under references:; its cached record is abstract-only. CONTENT. 12 pathophysiology nodes, all with biological_scale, forming a connected chain from the THRA dominant-negative variant (genetic_context.functional_impact_category: DOMINANT_NEGATIVE, zygosity HETEROZYGOUS, variant_origin GERMLINE) through persistent NCoR/SMRT corepressor occupancy at thyroid hormone response elements to transcriptional silencing of T3 target genes, then branching to six TR-alpha-dependent tissue nodes (skeletal maturation, GI motility, erythroid differentiation, cardiac chronotropic drive, skeletal muscle, CNS). A parallel branch records sparing of TR-beta tissues including the pituitary thyrotroph, the resulting discordant thyroid panel with non-elevated TSH, and escape from TSH-based newborn screening. Pathway-state claims use Descriptor.modifier (LOSS_OF_FUNCTION on the thyroid hormone receptor signaling pathway nodes, chosen over DECREASED because the claim is qualitative - the pathway is outside ligand control, not merely running low) while the variant-consequence claim uses GeneticContext.functional_impact_category, per the CLAUDE.md decision tree. Also: 15 HP-bound phenotypes with frequencies where sourced; 7 biochemical records with LOINC-coded reference_ranges and an HP:0033075 interpretation band on TSH; 3 definitions (one DIAGNOSTIC_CRITERIA, two PHENOTYPE_ALGORITHM with honest validation_status - UNVALIDATED for the anaemia filter that found no new cases in 6,540 children, PROPOSED for the fT3/fT4 centile screen); 2 treatments; 4 animal models with modeled_mechanisms, model_scale, limitations and (for the zebrafish) typed divergences; 3 differential diagnoses; 2 discussions (KNOWLEDGE_GAP on levothyroxine outcome benefit, HUMAN_MODEL_MISMATCH on whether the mouse NCOR1 rescue transfers). 21 references, 101 snippets. A deliberate negative result is curated rather than dropped: the target_mechanisms edge from Levothyroxine to the cardiac node carries supports: REFUTE, because thyroxine provably does not raise heart rate in RTH-alpha patients (PMID:37286550), which is what makes higher dosing tolerable. VALIDATION RUN, with results. just validate - passed (schema, terms, references). just validate-terms - passed. just count-verified-snippets - 101/101 verified. just validate-disorders (the authoritative batched gate) - passed, 101/101. just check-duplicate-keys, check-entity-refs, check-causal-targets, check-qualifier-terms, check-enum-values (path-scoped) - all passed. Whole-KB ungated text checks: check-folded-hyphens, check-snippet-length, check-title-snippets, check-snippet-grading, check-reference-titles - all passed. just normalize-cache and just check-term-cache-integrity - passed; the only cache rows added are GO:0002154, GO:0014831, MONDO:0013757, NCIT:C74786, NCIT:C74787, NCIT:C81968 plus their enum-membership rows. just compliance - 84.0% global, 84.2% weighted. check-qualifier-terms-online was NOT run because no qualifier term was added. check-environmental-evidence was NOT run because no environmental: block was added. just check-source-defect-claims is report-only and reports no finding in this file. check-folded-hyphens initially FAILED on one line of my own explanation prose ("postnatal corepressor-" split across a folded scalar) and was fixed by rephrasing. No baseline file was modified by this change. SELF-REVIEW CATCH. A first draft of the free T4 and free T3 notes described median analyte values from PMID:38148509 as RTH-alpha cohort values. They are not: they are medians for children selected by that study's screening filter, none of whom carried a THRA variant. Corrected so that no RTH-alpha cohort mean or median is asserted for either analyte. Separately, all 21 reference_title values were compared character-for-character against the title: frontmatter of their references_cache/ files - nothing validates that automatically - and all matched exactly. TERM AND IDENTIFIER PROVENANCE. hgnc:11796 was verified in both directions against the HGNC REST API (symbol THRA -> HGNC:11796 and hgnc_id 11796 -> THRA), per the CLAUDE.md warning that validate-terms checks a gene label against its CURIE but nothing against the gene the text names. HP, GO, CL, MONDO, NCIT and CHEBI terms were resolved via ols: adapters or the committed cache/<prefix>/terms.csv; no local MONDO/HP/NCIT database was built, per the run's disk constraint. The eight LOINC codes were resolved against the NLM Clinical Table Search Service; LOINC is not configured in conf/oak_config.yaml so they are hand-verified rather than gate-checked, and this is stated in the entry's notes:. DELIBERATE OMISSIONS, each with a reason recorded in the entry's notes:. No conforms_to - hypothyroidism_thyroid_hormone_deficiency is the mechanistic inverse of this disease (its chain starts at impaired hormone synthesis, which RTH-alpha does not have), the same call the RTH-beta entry made; defective_skeletal_mineralization was also read and rejected (its rate-limiting step is hydroxyapatite deposition, not chondrocyte maturation). A receptor-resistance module spanning RTH-alpha, RTH-beta, MCT8 deficiency and SECISBP2 deficiency is flagged as future work and was not created. No has_subtypes - the genotype-phenotype correlation is a severity gradient across a continuum of variants that no source partitions. No cell_types on the GI node, which is marked mechanism_confidence: PROVISIONAL, because nothing located names the responsible cell type in human disease. Hypercholesterolemia is deliberately left unconnected to any pathophysiology node because cholesterol handling is TR-beta territory and the route is unexplained. No reference-interval bounds for reverse T3, creatine kinase, haemoglobin or MCV. TSH bound to the NCIT analyte term NCIT:C2280 because NCIT has no TSH measurement term matching NCIT:C74786/C74787. No ORPHA evidence, because the Orphadata bulk XML is absent from this checkout and fetching it was out of scope - so the Orphanet prevalence figures are mentioned in notes: as uncited rather than quoted. No clinical_trials and no datasets, none located. Skin tags, decreased metabolic rate and pericardial effusion not curated as phenotypes for want of more than single-series or uncited support.

Claude Code ▸

Resistance to Thyroid Hormone Alpha (RTHα) — Comprehensive Research Report

claude-haiku-4-5-20251001, claude-sonnet-5 25 citations 2026-09-10T18:29:24.396260

Resistance to Thyroid Hormone Alpha (RTHα) — Comprehensive Research Report

MONDO:0013757 | OMIM #614450 (listed as Hypothyroidism, Congenital, Nongoitrous, 6; CHNG6) | Gene: THRA (HGNC:11796, OMIM 190120, 17q21.1) | Orphanet: ORPHA 566231 | ICD-10: E07.8 (Other specified disorders of thyroid) | Category:* Mendelian, autosomal dominant

1. Disease Information

Overview. Resistance to thyroid hormone alpha (RTHα) is a rare autosomal dominant disorder caused by heterozygous, dominant-negative loss-of-function variants in THRA, the gene encoding thyroid hormone receptor alpha (TRα). Unlike classic "generalized" resistance to thyroid hormone (RTHβ, caused by THRB mutations), RTHα produces tissue-specific hypothyroidism confined largely to TRα1-expressing tissues (CNS, heart, gut, skeletal muscle, bone, erythroid precursors), while thyroid function tests remain near-normal because the hypothalamic-pituitary-thyroid feedback axis is governed by TRβ, which is unaffected. The first case was reported by Bochukova et al. in 2012 (PMID:22168587, N Engl J Med), describing a child with classic clinical features of hypothyroidism (growth retardation, developmental delay, skeletal dysplasia, severe constipation) but only borderline-abnormal thyroid function tests; whole-exome sequencing identified a de novo heterozygous nonsense variant (c.1207G>T, p.Glu403X) that "generated a mutant protein that inhibited wild-type receptor action in a dominant negative manner."

Only ~41 cases from ~28 families had been published in the literature as of the most recent comprehensive review period (2020–2024), making it an ultra-rare condition that is likely substantially underdiagnosed because, unlike RTHβ, standard thyroid function tests are not distinctive (van Mullem et al., Best Pract Res Clin Endocrinol Metab 2015, PMID:26303090).

Identifiers: - OMIM #614450 (CHNG6) - OMIM gene *190120 (THRA) - Orphanet ORPHA566231 - MONDO:0013757 - HGNC:11796 (THRA) - ICD-10: E07.8 - MeSH: THRA is indexed under "Thyroid Hormone Resistance Syndrome" (no disease-specific MeSH heading yet exists for RTHα specifically; it is typically captured under the RTH parent term)

Synonyms: Resistance to thyroid hormone due to a mutation in thyroid hormone receptor alpha; RTHα; THRA-related resistance to thyroid hormone; Congenital nongoitrous hypothyroidism 6 (CHNG6); Thyroid hormone resistance, alpha.

Evidence base: Nearly all data derive from individual case reports and small case series (aggregated in narrative and systematic reviews) rather than large epidemiologic cohorts or EHR-derived data, reflecting the condition's rarity (~41 published cases worldwide).

2. Etiology

Disease Causal Factors. RTHα is a purely genetic, monogenic disorder: heterozygous dominant-negative variants in THRA are both necessary and sufficient to cause the phenotype. There is no known environmental, infectious, or purely mechanistic (non-genetic) causal pathway.

Genetic risk factors: - Heterozygous THRA variants affecting the ligand-binding domain (LBD) (most reported variants) or, less commonly, variants affecting both TRα1 and the non-hormone-binding TRα2 isoform. - De novo occurrence is common; ~6 of the reported variants have been inherited from an affected parent, consistent with autosomal dominant transmission with full penetrance but markedly variable expressivity (van Mullem 2015, PMID:26303090; JCRPE clinical spectrum review 2021, PMC7947725). - Genotype severity correlates loosely with variant class: frameshift/premature-stop variants → more severe phenotype; missense variants → generally milder phenotype, though there is documented intrafamilial variability even with an identical missense variant (Nauwynck et al., Horm Res Paediatr 2026, PMID:42301959 — a mother and two daughters sharing c.1207G>A showed markedly different severity, "cannot be predicted by genotype alone").

Environmental risk factors: None established. There is no evidence that toxins, diet, occupational exposure, or perinatal factors modify risk of developing RTHα (it is not multifactorial).

Protective Factors: No protective genetic or environmental factors have been identified in the literature (the disease is fully penetrant for at least some phenotypic feature once the causal variant is present).

Gene-Environment Interactions: Not applicable/not reported; no GxE interaction data exist for this ultra-rare Mendelian disorder.

3. Phenotypes

The clinical picture is one of selective, tissue-specific hypothyroidism. Frequencies below are drawn from the JCRPE 2021 systematic clinical-spectrum review of published cases (PMC7947725) unless noted.

Neurodevelopmental / Behavioral

Delayed motor and speech milestones — ~85% (34/40 cases). HPO: Motor delay (HP:0001270), Delayed speech and language development (HP:0000750)
Dyspraxia / ataxic, broad-based gait, slow dysarthric speech — described as a major source of disability across ages. HPO: Dysdiadochokinesis/ Gait ataxia (HP:0002066), Dysarthria (HP:0001260)
Intellectual disability, variably reduced IQ — HPO: Intellectual disability (HP:0001249)
Autism spectrum features / ASD-associated variants — 6 THRA variants identified among 30 children screened in ASD cohorts (Kalikiri et al., Autism Res 2017, PMID:28856816). HPO: Autistic behavior (HP:0000729)
Seizures — reported in a minority of cases. HPO: Seizure (HP:0001250)

Growth / Skeletal

Short stature / growth retardation — ~60% (12/20 children), lowest height SD score −3.1. HPO: Short stature (HP:0004322)
Relative macrocephaly — ~70% (23/33). HPO: Macrocephaly (HP:0000256)
Delayed bone age / skeletal dysplasia / epiphyseal dysgenesis (childhood-specific; resolves in adulthood). HPO: Delayed skeletal maturation (HP:0002750), Epiphyseal dysplasia (HP:0002656)
Wormian bones (serpiginous cranial sutures, delayed fontanelle closure) — 32% (10/31). HPO: Wormian bones (HP:0002645)
Delayed tooth eruption — 44% (8/18 children). HPO: Delayed eruption of teeth (HP:0000684)
Short/broad facies, hypertelorism, flattened nose, macroglossia, thick lips (coarse facial gestalt) in ~one-third. HPO: Coarse facial features (HP:0000280), Macroglossia (HP:0000158)
Thickened calvarium / cortical hyperostosis / increased bone mineral density — characteristic in adults. HPO: Cranial hyperostosis (HP:0004437)
Short limbs, disproportionate short stature — reported in untreated adults (Bauer Westbye et al., J Endocr Soc 2023, PMID for bvad089 not captured in this pass)

Gastrointestinal

Chronic constipation — 84% (26/31) — one of the most consistent findings across the lifespan, attributed to decreased colonic peristalsis (documented by manometry). HPO: Constipation (HP:0002019)
Umbilical/inguinal hernias reported.

Dermatologic

Skin tags and moles (acrochordons), more prominent in adults — 21% (7/33). HPO: Skin tags (HP:0010701)
Rough, dry, thickened skin, particularly in children.

Hematologic

Mild, usually normocytic anemia — 77% (23/30); near-universal feature, unresponsive to hematinics, with normal iron/B12/folate (van Gucht et al., J Clin Endocrinol Metab 2017, PMID:28911146). HPO: Normocytic anemia (HP:0001923)

Cardiovascular / Metabolic

Bradycardia, abnormal sympathovagal balance, cardiac contractility indices in the hypothyroid range. HPO: Bradycardia (HP:0001662)
Rare cardiomyopathy (3 cases) and pericardial effusion (1 case) reported.
Low resting metabolic rate. HPO: Decreased basal metabolic rate (HP:0008977, if applicable — verify against enum)
Hepatic steatosis reported in adult cases (Nauwynck 2026).
Elevated LDL cholesterol. HPO: Hypercholesterolemia (HP:0003124)

Laboratory abnormalities

Elevated muscle creatine kinase — 73% (8/11 untreated children), range 218–981 U/L; proposed as a pediatric diagnostic biomarker.
Characteristic thyroid profile (see Section 4/biochemistry).

Phenotype characteristics: - Age of onset: Typically present from infancy/early childhood (growth faltering, developmental delay noted in first years of life); a subset of adult-onset features (tachycardia, hepatic steatosis, social/learning difficulties) may only become apparent or be recognized retrospectively in adulthood. - Severity: Highly variable — ranges from severely affected children (frameshift variants) to adults with mild learning difficulties who attended university untreated. - Progression: The "clinical picture or laboratory findings becom[e] less remarkable with age" in several domains (e.g., epiphyseal dysgenesis present in childhood is absent in adult imaging), but anemia, constipation, and cognitive effects can persist into adulthood. - Frequency: See percentages above (JCRPE 2021 review, n≈40 cases).

Quality-of-life impact: Motor dyspraxia, dysarthric speech, chronic constipation, fatigue, low mood, social dysfunction, and learning disabilities requiring educational support are reported to meaningfully affect daily functioning in both children (school performance) and untreated adults (concentration problems, excessive daytime sleepiness, social dysfunction) (Bauer Westbye/JES 2023 untreated-adult cohort).

4. Genetic/Molecular Information

Causal gene: THRA (HGNC:11796; OMIM *190120), chromosome 17q21.1.

Gene structure/isoforms: THRA produces two principal splice isoforms: - TRα1 — the biologically active, T3-binding nuclear receptor; high expression in CNS, myocardium, GI tract, skeletal muscle, bone. Molecular function: GO:0004887 (thyroid hormone receptor activity). - TRα2 — lacks a functional ligand-binding domain due to alternative C-terminal splicing; does not bind T3 but retains DNA-binding capacity and may act as an endogenous inhibitor of TRα1 signaling. RNA-seq data indicate TRα2 strongly predominates over TRα1 in the developing and adult human brain, a point relevant to interpreting variants that differentially affect the two isoforms.

Pathogenic variant spectrum (as of 2024 review, ~25 distinct variants across ~28 families): - Missense variants — most common class; generally milder phenotype; concentrated in the ligand-binding domain. - Examples with published functional characterization: - p.Glu403X (c.1207G>T) — the index Bochukova 2012 nonsense variant (PMID:22168587). - p.Ala263Val (A263V) — affects both TRα1 and TRα2; homologous to the RTHβ-causing THRB A317V variant; transcriptionally impaired at low T3 but function was restorable at higher hormone concentrations, "revers[ing] its dominant negative inhibitory activity" — a nuance relevant to high-dose therapy rationale. - p.Asn359Tyr (N359Y) — de novo, affects both isoforms; dominant-negative for TRα1, weaker dominant-negative effect for TRα2, especially when co-expressed with normal TRβ1. - p.Arg384Cys (R384C) — identified via whole-genome sequencing in an autism cohort; shown to be functionally deleterious in murine TRα1; transgenic mice exhibited aberrant GABAergic interneuron development and behavioral abnormalities that were reversible with thyroid hormone treatment initiated even in adulthood. - p.Asp268Asn — reported with early levothyroxine treatment and outcome data (J Pediatr Endocrinol Diabetes, recent case report). - p.Arg417Ter (c.1249C>T) and p.Glu173Gly (c.518A>G) — both logged in ClinVar under "Congenital nongoitrous hypothyroidism 6." - A synonymous substitution (c.1044G>T) was found in one autism cohort case, of uncertain pathogenicity for classic RTHα. - Frameshift variants — 3 reported variants affecting 4 cases, associated with the most severe phenotypes. - Nonsense/premature stop variants — 3 distinct variants.

Variant classification (ACMG/AMP): Per ClinVar, reported variants are generally classified Pathogenic/Likely Pathogenic for "Congenital nongoitrous hypothyroidism 6." Functional (in vitro transactivation/dominant-negative) assays are typically required to confirm pathogenicity of novel missense variants given the absence of a distinctive biochemical signature.

Variant origin: All reported RTHα cases are germline, heterozygous. No somatic THRA RTHα has been described (contrast with oncology literature in which THRA/TRα dysregulation — not classic RTHα missense variants — has been separately studied in some cancers; not relevant to this germline syndrome).

Allele frequency in population databases: THRA is under strong purifying selection for loss-of-function in gnomAD (constrained gene); reported RTHα pathogenic missense/truncating variants are essentially absent from population databases (gnomAD/ExAC/1000 Genomes), consistent with de novo origin and dominant pathogenicity — precise per-variant gnomAD frequencies were not captured in this pass and should be verified directly in gnomAD/ClinVar at curation time.

Functional consequence — mechanism: Dominant-negative loss of function. The mutant TRα1 protein retains DNA-binding and corepressor-binding capacity but fails to release corepressor complexes (NCoR1/SMRT + histone deacetylase, HDAC) upon T3 binding, resulting in "constitutive binding of mutant TR to corepressors, with failure of corepressor dissociation and coactivator recruitment following T3 occupancy," which "likely mediates dominant negative inhibition" over the co-expressed wild-type allele and, where relevant, TRβ (van Mullem 2015, PMC4559105).

Modifier genes: None formally established; authors speculate that "additional factors, possibly cofactor proteins" (e.g., corepressor/coactivator stoichiometry) contribute to the marked phenotypic variability seen even among carriers of an identical variant (intrafamilial variability, Nauwynck 2026).

Epigenetic information: No disease-specific DNA methylation/histone studies of patient tissue have been published; however, the core molecular mechanism is itself an epigenetic one at target-gene promoters — mutant TRα1 causes "constant HDAC-induced chromatin remodeling" that sustains transcriptional repression of T3 target genes even when hormone is present (mechanistic basis for HDAC-inhibitor experimental therapy, see Section 12).

Chromosomal abnormalities: No large structural/chromosomal (aneuploidy, translocation, CNV) etiology has been reported for RTHα; all reported cases are point variants (missense, nonsense, frameshift) within THRA.

5. Environmental Information

RTHα is a purely monogenic disorder. No environmental toxins, occupational exposures, lifestyle factors, or infectious agents have been implicated as causal or disease-modifying in the literature reviewed. This section is not applicable beyond noting that iodine status and maternal thyroid status during pregnancy are not reported to influence phenotype expression in THRA variant carriers (distinct from acquired thyroid disease).

6. Mechanism / Pathophysiology

Ordered causal chain

A heterozygous THRA variant (missense in the ligand-binding domain, or frameshift/nonsense) leads to expression of a mutant TRα1 protein (and, for variants upstream of the TRα2-specific exon, mutant TRα2) that retains DNA- and corepressor-binding activity but cannot release corepressor upon T3 binding.
This mutant receptor results in a dominant-negative effect: it competes with and suppresses the transcriptional activity of the co-expressed wild-type TRα1 allele (demonstrated mechanism) in TRα1-predominant tissues.
Constitutive corepressor (NCoR1/SMRT) and HDAC binding leads to persistent chromatin compaction at T3-responsive target gene promoters, i.e., a state of molecular/cellular hypothyroidism at the target-gene transcription level, despite near-normal circulating T3/T4 — this is the "tissue-specific hypothyroidism" hallmark of RTHα (inferred primarily from animal/in vitro reporter and chromatin studies, extrapolated to human disease).
Because the hypothalamic-pituitary-thyroid axis senses hormone levels predominantly via TRβ (which is unaffected), the pituitary/hypothalamus do not perceive tissue hypothyroidism, so TSH fails to rise compensatorily — explaining the near-normal-to-low-normal TSH and the diagnostic pitfall of relying on standard thyroid function tests.
In parallel, peripheral deiodinase handling is shifted (reduced TRα-mediated negative regulation of deiodinase activity is hypothesized), resulting in the characteristic biochemical signature: low/low-normal free T4, high/high-normal free T3, low/low-normal reverse T3, and an abnormally low FT4/FT3 ratio (directly demonstrated biochemically in patients; deiodinase-level mechanism is partly inferred).
In the CNS (where TRα1 — and especially TRα2 — predominates developmentally), impaired T3 target gene activation leads to abnormal neuronal/glial maturation, including — in the R384C mouse model — "aberrant development of GABAergic inhibitory interneurons," which manifests clinically as delayed motor/speech milestones, dyspraxia, ataxic gait, intellectual disability, and (in some cases) ASD features and seizures. This step is directly demonstrated in a murine model and inferred to extend to humans by phenotypic analogy.
In the growth plate/skeleton, dominant-negative TRα1 signaling causes delayed chondrocyte maturation and epiphyseal dysgenesis in childhood, resulting in short stature, delayed bone age, delayed tooth eruption, and the wormian-bone/cranial-suture phenotype; with skeletal maturation proceeding anomalously into adulthood as thickened calvarium/cortical hyperostosis and increased bone mineral density (demonstrated in both human imaging series and the Thra1^PV/+ mouse model).
In the gastrointestinal tract, impaired TRα1 signaling in enteric smooth muscle/neurons leads to decreased colonic peristalsis, manifesting as the near-universal chronic constipation.
In bone marrow erythroid progenitors, TRα1 dysfunction impairs the balance between proliferation and differentiation: patient-derived human erythroid progenitor cells (HEPs) show delayed spontaneous differentiation (~2 days later than controls), larger cell size, reduced glycophorin A (CD235a, a terminal differentiation marker) and increased c-Kit (CD117, a proliferation marker); exogenous T3 still accelerates differentiation in both control and patient cells, implying reduced (not absent) hormone sensitivity rather than complete unresponsiveness — resulting in the near-universal mild normocytic anemia (van Gucht 2017, PMID:28911146, direct human cell evidence).
In cardiac and skeletal muscle, TRα1 dysfunction results in reduced basal metabolic rate, bradycardia with abnormal sympathovagal balance, and elevated muscle creatine kinase — indices consistent with a tissue-level hypothyroid state that is relatively resistant to correction by standard-dose levothyroxine (see Treatment, Section 12), suggesting either incomplete T3 delivery/activation or genuinely reduced receptor responsiveness even at higher local hormone levels in these tissues.
Hepatic involvement (steatosis, elevated LDL/HDL ratio) has been reported in adult cases and is consistent with TRα1's role in lipid/metabolic regulation, though the liver is traditionally considered more TRβ-dominant — this cross-tissue effect is less well mechanistically characterized and should be considered a partially inferred branch of the pathway.

Molecular pathways

Canonical thyroid hormone receptor signaling (nuclear receptor transcriptional regulation): GO:0006355 (regulation of DNA-templated transcription) downstream of GO:0004887 (thyroid hormone receptor activity).
NCoR1/SMRT-HDAC corepressor pathway: central to the dominant-negative mechanism — GO:0035035 (histone acetyltransferase binding) / corepressor-related GO terms.

Cellular processes

Impaired erythroid progenitor proliferation/differentiation balance (GO:0030218, erythrocyte differentiation).
Impaired chondrocyte/osteoblast maturation in growth plate (relevant to skeletal dysplasia).
Altered GABAergic interneuron development in cortex (murine R384C model).

Protein dysfunction

Loss-of-function/dominant-negative missense or truncating changes in the TRα1 ligand-binding domain (helix 12 disruption in the mouse PV model prevents T3 binding/coactivator recruitment) or DNA-binding domain; UniProt P10827 (THRA/TRα). No protein aggregation/misfolding mechanism — this is a transcription-factor dominant-negative disorder, not a proteopathy.

Biochemical abnormalities

Characteristic pattern: low/low-normal FT4, high/high-normal FT3, low FT4/FT3 ratio, low/low-normal reverse T3, normal TSH, elevated CK (children especially), mild normocytic anemia, elevated LDL/total cholesterol, low/low-normal IGF-1, elevated IL-8 (pro-inflammatory).

Molecular profiling / advanced technologies

RNA-seq data show TRA2 isoform predominance over TRα1 in developing/adult human brain (relevant to interpreting CNS phenotype severity by variant location).
No large-scale patient transcriptomic, proteomic, or single-cell atlases specific to RTHα patient tissue were identified in this search pass; most molecular data derive from reporter-gene assays, patient-derived erythroid progenitor cultures, and murine/zebrafish models rather than from GEO/ArrayExpress patient cohorts.

Suggested ontology terms: - GO biological processes: GO:0006355 (regulation of transcription), GO:0030218 (erythrocyte differentiation), GO:0001501 (skeletal system development), GO:0007416 (synapse assembly, for GABAergic interneuron defect) - GO molecular function: GO:0004887 (thyroid hormone receptor activity) - Cell types (CL): CL:0000765 (erythroblast), CL:0000038 (erythroid progenitor cell), CL:0000138 (chondrocyte), CL:0000617 (GABAergic interneuron), CL:0000187 (myocyte), CL:0000216 (Sertoli cell — relevant to gonadal expression studies)

7. Anatomical Structures Affected

Organ level: - Primary: Central nervous system (brain), skeletal system (growth plate, calvarium, teeth), gastrointestinal tract (colon), hematopoietic system (bone marrow/erythroid lineage), cardiovascular system (heart). - Secondary: Liver (steatosis, lipid abnormalities reported in adults), skin (skin tags, dry/thickened skin). - Body systems: Endocrine, nervous, musculoskeletal, digestive, hematologic, cardiovascular.

Tissue/cell level: - Colonic smooth muscle/enteric neurons (constipation). - Growth-plate chondrocytes, osteoblasts/osteoclasts (skeletal dysplasia, increased cortical bone). - Erythroid progenitor cells in bone marrow (anemia). - Cortical GABAergic interneurons (murine model; presumptive human analog). - Cardiac myocytes (bradycardia, reduced contractility indices). - Skeletal muscle (elevated CK).

Subcellular level: - Nucleus — GO:0005634 (nucleus); TRα1 acts as a nuclear hormone receptor/transcription factor at target-gene promoters, with corepressor complexes recruiting HDAC to chromatin (GO:0000118, histone deacetylase complex).

Localization (UBERON): - UBERON:0000955 (brain), UBERON:0001968 (skeletal system), UBERON:0001155 (colon), UBERON:0002371 (bone marrow), UBERON:0000948 (heart), UBERON:0002107 (liver). - Lateralization: Not applicable; RTHα is a systemic, bilateral/symmetric disorder with no laterality pattern reported.

8. Temporal Development

Onset: Congenital/early-childhood onset for most features (growth faltering, developmental delay, delayed bone age typically recognized in infancy–early childhood); some features (hepatic steatosis, learning/social difficulties, tachycardia) are reported or first characterized in adulthood, either as persistence/evolution of the childhood phenotype or as later recognition in previously undiagnosed mild cases (e.g., the mother in the Nauwynck 2026 kindred).

Onset pattern: Insidious/chronic rather than acute — there is no described acute crisis presentation (contrast with, e.g., thyroid storm in Graves disease).

Progression: - Several skeletal features (epiphyseal dysgenesis) that are prominent in childhood are not present in adult imaging — i.e., some aspects of the phenotype attenuate with growth-plate closure. - Conversely, thickened calvarium/cortical hyperostosis and increased bone mineral density become more prominent in adults. - Anemia, constipation, and neurocognitive effects can persist through adulthood. - Overall the disease course is stable-to-slowly-evolving rather than progressive/degenerative; it is not described as a relapsing-remitting condition.

Disease duration: Chronic, lifelong — there is no spontaneous remission described, though the clinical and biochemical picture tends to become "less remarkable" with age in several (not all) domains.

Critical periods: Early childhood appears to be a critical window for neurodevelopmental intervention — case reports emphasize that "early treatment initiation yields more distinguishable developmental benefits," paralleling the R384C mouse data showing some interneuron/behavioral abnormalities are reversible with T3 treatment even in adulthood but presumably with better outcomes if treated early.

9. Inheritance and Population

Epidemiology: - Prevalence: Orphanet lists RTHα as prevalence <1 in 1,000,000 (ultra-rare). Approximately 41 cases across ~28 families have been published in the literature as of the most recent reviews (2021–2024), though the disorder is considered underdiagnosed given the non-distinctive standard thyroid panel. - Incidence: Not formally estimated in any population-based registry; no birth-prevalence studies exist.

Inheritance pattern: Autosomal dominant, with dominant-negative molecular mechanism. Most cases are de novo; at least 6 of the published variants have been transmitted from an affected parent, confirming vertical transmission is possible and documented.

Penetrance: Appears to be high/complete for at least some phenotypic feature (all reported heterozygous carriers show some abnormality), but with markedly incomplete and variable expressivity — severity is not predictable from genotype alone, as demonstrated by intrafamilial variability with an identical variant (Nauwynck 2026).

Expressivity: Highly variable, even within families carrying the identical missense variant — documented biochemical attenuation in an affected mother compared to her more severely affected daughters, and clinical heterogeneity (only one of two affected sisters had constipation and delayed dentition).

Genetic anticipation: Not reported/described for RTHα (not a repeat-expansion disorder).

Germline mosaicism: Not specifically documented in the literature reviewed, though it remains a theoretical consideration for any de novo dominant disorder when counseling families with an apparently de novo proband.

Founder effects: None reported; variants identified to date are private/family-specific rather than recurrent founder alleles in specific populations.

Consanguinity: Not implicated — consistent with a dominant (not recessive) mechanism.

Carrier frequency: Not applicable in the traditional sense (autosomal dominant, not a recessive carrier state); population databases (gnomAD) show the gene to be constrained, with disease-causing variants essentially absent from the general population.

Population demographics: - No specific ethnic or geographic enrichment has been established; cases have been reported from Europe (UK, Netherlands, Belgium, Scandinavia), the Middle East/North Africa (first MENA case report, PMC7897355), and elsewhere — consistent with a panethnic, privately-occurring de novo disorder rather than one with population-specific founder variants. - Sex ratio: Not clearly skewed in the literature; both males and females are affected (the described kindreds include affected mother-daughter pairs and isolated cases of both sexes). - Age distribution: Spans neonatal/infantile presentation through adulthood (documented adult cohort up to at least the 4th–5th decade, e.g., the untreated-adult J Endocr Soc cohort and 17-year follow-up case report).

10. Diagnostics

Clinical/laboratory tests: - Thyroid function panel (FT4, FT3, TSH, reverse T3) — the key diagnostic clue is low/low-normal FT4 + high/high-normal FT3 + normal TSH, yielding a low FT4/FT3 ratio and a high T3/rT3 ratio; reverse T3 is characteristically low/low-normal. Crucially, TSH is not elevated (distinguishing it from primary hypothyroidism and from RTHβ, where TSH is typically elevated/inappropriately normal with high T4). LOINC analytes: Free T4, Free T3, TSH, Reverse T3. - Creatine kinase (CK) — elevated in the majority of untreated children (73%, range 218–981 U/L); proposed as a pediatric screening/diagnostic biomarker, though normal in most untreated adults. - Complete blood count — mild normocytic (occasionally macrocytic) anemia with normal iron/B12/folate. - Lipid panel — elevated total/LDL cholesterol, elevated LDL/HDL ratio. - Imaging — skeletal survey/plain films for wormian bones, delayed bone age (childhood), thickened calvarium/cortical hyperostosis, increased bone mineral density (adulthood); dental films for delayed tooth eruption. - Colonic manometry has been used in at least one case to document decreased peristalsis underlying constipation.

Genetic testing: - Targeted THRA sequencing (single-gene test) is the most direct confirmatory test once RTHα is clinically suspected given a compatible biochemical pattern. Available through the NIH Genetic Testing Registry (GTR) for THRA (NCBI GTR Gene ID 7067). - Exome or genome sequencing has been the primary discovery route for nearly all reported cases (including the index Bochukova 2012 case and the R384C autism-cohort case), and remains appropriate given the nonspecific/attenuated biochemical phenotype that often does not trigger a targeted single-gene order. - Panel testing: RTHα should be considered in broader "thyroid hormone resistance" or "congenital hypothyroidism" NGS panels, and in intellectual-disability/neurodevelopmental gene panels given the overlap with developmental-delay presentations. - Chromosomal microarray/karyotype/FISH: Not relevant — RTHα is caused by point variants (missense/nonsense/frameshift), not copy-number or structural chromosomal changes; CMA/karyotype would be expected to be normal and is not a primary diagnostic tool for this condition.

Clinical criteria: No formal consensus diagnostic criteria (e.g., DSM/ICD-style) have been published; diagnosis rests on the combination of compatible phenotype + characteristic (if subtle) thyroid-hormone pattern + confirmatory THRA genetic testing.

Differential diagnosis: Primary congenital hypothyroidism, RTHβ (THRB-mediated generalized thyroid hormone resistance — distinguished by elevated TSH and high total T4/T3), other causes of short stature/developmental delay with skeletal dysplasia (e.g., skeletal dysplasia syndromes, other syndromic intellectual disability), and isolated chronic constipation of other etiology. Autism spectrum disorder of other genetic cause should also be considered, given the overlap with THRA variants found in ASD sequencing cohorts.

Screening: No newborn-screening program currently screens for RTHα (unlike primary congenital hypothyroidism, which is detected by TSH-based newborn screening — a modality that would miss RTHα because TSH is normal). Cascade family screening (biochemical + genetic) is recommended once a proband is identified, given documented intrafamilial transmission and variable expressivity (Nauwynck 2026 explicitly recommends "family-based genetic evaluation and cascade screening across lifespans").

11. Outcome/Prognosis

Survival/mortality: No excess mortality has been reported; RTHα is not described as life-limiting in published cases. No survival-rate or life-expectancy data exist (consistent with a non-lethal, chronic disorder), though systematic long-term outcome data are sparse given the small number of cases.

Morbidity/function: - Chronic constipation, dyspraxia/motor incoordination, dysarthric speech, variable intellectual disability, and social/learning difficulties are the dominant sources of disease-related disability. - Fertility appears unaffected: regular pregnancies have been reported in untreated affected females. - One untreated adult attended university despite mild childhood developmental delays, illustrating the wide severity range.

Disease course: - Complications include persistent anemia (often treatment-refractory), possible hepatic steatosis in adulthood, and — rarely — cardiomyopathy or pericardial effusion. - Recovery/improvement potential with treatment is domain-specific (see Section 12): neurodevelopmental/behavioral and GI symptoms respond better than growth, cardiac, and hematologic parameters.

Prognostic factors: - Variant type (frameshift/truncating → more severe) is the most consistently cited prognostic factor. - Age at treatment initiation — earlier initiation of levothyroxine is associated with more distinguishable developmental benefit. - Tissue-specific TRα expression and (speculative) cofactor/corepressor stoichiometry differences likely contribute to the unexplained intrafamilial variability.

Prognostic biomarkers: Elevated CK in childhood has been proposed as a biomarker correlating with disease activity/severity, though this is not validated as a formal prognostic tool; no molecular prognostic biomarker panel currently exists.

12. Treatment

Pharmacotherapy — Levothyroxine (LT4): - LT4 has been "the first choice to date" and is the mainstay of treatment, typically dosed above what would be used for standard primary hypothyroidism to attempt to overcome TRα resistance in affected tissues, producing a biochemical pattern resembling central-hypothyroidism treatment (rise in FT3/FT4 with TSH suppression). NCIT term: NCIT:C15986 (Pharmacotherapy); therapeutic agent — CHEBI levothyroxine, or NCIT drug term for Levothyroxine. - Clinical benefits documented: improvement in constipation (majority of cases), motor coordination, alertness, school performance, concentration, motivation, hypotonia, accelerated neuromotor development in children treated early, improved dyspraxia and social interaction in adults, reduction in elevated LDL cholesterol and muscle CK, and increases in IGF-1 and SHBG. - Limited/no response: Anemia is largely unresponsive to LT4. Linear growth shows only limited benefit. Cardiac parameters (heart rate, contractility indices) and resting energy expenditure/muscle CK are comparatively poorly responsive relative to the degree of biochemical (FT3/FT4) correction achieved — i.e., tissues show differential sensitivity to exogenous hormone even at supraphysiologic FT3 exposure. - Safety concern: Because TSH readily suppresses with LT4 while some TRα-dependent tissues remain resistant, patients can develop supraphysiologic FT3 levels — raising concern for "unwanted toxicities in normal TRβ-containing tissues" (e.g., theoretical cardiac/bone risk from chronic T3 excess in tissues where TRβ signaling is intact), a safety tension unique to treating a receptor-specific resistance syndrome with a non-selective hormone. - Liothyronine (T3): used in at least one atypical case, associated with cardiac/metabolic response; generally considered a second-line or individualized option given the already-elevated endogenous FT3 in most patients.

Pharmacogenomics: No THRA-specific pharmacogenomic (drug-metabolism) data were identified; this is a receptor-resistance disorder rather than a drug-metabolism disorder, so conventional PharmGKB-style variant-drug interaction data are not applicable in the usual sense.

Advanced therapeutics (experimental / preclinical): - TRα1-selective thyromimetics are proposed as the ideal future approach — compounds that would selectively activate residual normal TRα1 (or partially-functional mutant TRα1) in TRα-predominant tissues while sparing TRβ-dominant tissues from toxicity. None are yet in human trials for RTHα specifically; existing thyromimetic development (e.g., sobetirome, a TRβ-selective agonist developed for dyslipidemia/demyelinating disease, and resmetirom, approved for MASH) is TRβ-selective and thus not directly applicable/may be the wrong receptor target for RTHα. - Corepressor/HDAC-pathway targeting: Because the core molecular lesion is failure to release the NCoR/SMRT-HDAC corepressor complex, genetic disruption of NCoR-TR interaction or pharmacologic HDAC inhibition has been tested in the murine Thra1^PV/+ model with conflicting results across studies — an earlier study (Subramanian et al., Hum Mol Genet 2014, PMID:24381310) reported the HDAC inhibitor SAHA (vorinostat) improved growth and bone development in Thra1^PV/+ mice, while a later, more detailed skeletal-phenotyping study (Freudenthal et al., Thyroid 2019, PMC6533791) found SAHA had "no beneficial or detrimental effects on bone structure, mineralization, or strength" and concluded SAHA treatment was "unlikely to improve the skeletal manifestations of RTHα" — an explicit model-divergence worth flagging in any curated entry (conflicting computational/animal-model evidence on the same pharmacologic strategy). - Gene therapy / RNA-based therapy / cell therapy / immunotherapy: None reported or in development specific to RTHα (not relevant given the dominant-negative, gain-of-repressive-function mechanism, which would require allele-selective silencing rather than simple gene replacement — no such approach has been published for this condition).

Surgical/interventional: Not applicable — RTHα has no surgical treatment indication.

Supportive/rehabilitative: - Physical/occupational/speech therapy for dyspraxia, gross/fine motor incoordination, and dysarthric speech (NCIT:C15302 Physical Therapy). - Dietary/laxative management of chronic constipation. - Educational support for learning disabilities.

Experimental treatment registries: A deep genotyping/phenotyping patient registry, DEEPTYPE — "Register for Patients With Thyroid Hormone Resistance" (ClinicalTrials.gov NCT06566066), is an active, ongoing registry study (estimated primary completion ~2029) intended to better characterize thyroid hormone resistance syndromes (including presumably RTHα) — full protocol detail (sponsor, eligibility specifics) could not be retrieved in this research pass and should be verified directly on ClinicalTrials.gov before citing as evidence.

Treatment outcomes / adverse events: No FAERS-level pharmacovigilance data exist specific to LT4 use in RTHα (too rare); adverse-event concerns are inferred mechanistically (supraphysiologic FT3 exposure risk) rather than empirically demonstrated in large cohorts.

Treatment algorithm / personalized medicine: No formal clinical practice guideline exists; management is individualized, typically involving endocrinology-led titration of LT4 (sometimes supplemented with T3) guided by clinical response (growth, constipation, developmental progress) more than by strict biochemical targets, given the blunted/variable biochemical-to-clinical correlation described above.

13. Prevention

Because RTHα is caused by de novo or inherited dominant germline variants with no known environmental trigger, classic primary prevention (risk-factor modification, vaccination) and public-health/environmental interventions are not applicable.

Secondary prevention (early detection): Cascade genetic/biochemical screening of first-degree relatives of an identified proband is explicitly recommended in the literature (Nauwynck 2026) given documented familial transmission and variable expressivity — early identification in an asymptomatic/mildly symptomatic relative could in principle allow earlier initiation of supportive and thyroid-hormone interventions, though no formal screening protocol or outcome data for this strategy were identified.
Genetic counseling: Recommended for identified families — autosomal dominant inheritance with a ~50% transmission risk to offspring of an affected parent, but with emphasis on the unpredictability of phenotypic severity (NCIT:C15240, Genetic Counseling).
Prenatal/preimplantation genetic testing: Not specifically reported as used for RTHα in the literature reviewed, though it would be technically available once a familial pathogenic variant is known (standard for autosomal dominant single-gene disorders).
Newborn screening: Current TSH-based newborn congenital-hypothyroidism screening programs will not detect RTHα (TSH is normal), which is explicitly identified in the literature as a major reason for underdiagnosis; no RTHα-specific newborn screening assay currently exists.
Prophylaxis: Not applicable (no known preventable trigger).

14. Other Species / Natural Disease

Taxonomy: No naturally-occurring (spontaneous) RTHα has been reported in companion animals or wildlife (e.g., no OMIA entry for spontaneous THRA RTHα disease was identified in this pass). All non-human data derive from engineered/induced genetic models (see Section 15), not naturally occurring veterinary disease.

Gene orthology: Thra is highly conserved; mouse Thra (MGI:98743) and zebrafish thraa/thrab (duplicated paralogs, reflecting teleost genome duplication) are the principal orthologs exploited for modeling.

Comparative biology: The corepressor-release mechanism of TRα1 dominant-negative action is conserved from fish to mammals, supporting cross-species extrapolation of mechanistic findings, though the existence of a duplicated thra locus in zebrafish (thraa/thrab) is a structural divergence from the single-copy human/mouse gene that must be considered when interpreting zebrafish dominant-negative results (a single thra paralog's mutation may be partially compensated by the other).

Zoonotic/transmission relevance: Not applicable — this is a non-infectious, non-transmissible genetic disorder.

15. Model Organisms

Mouse models: - Thra1^PV/+ knock-in mouse — the principal, most extensively characterized model. The PV mutation is a C-insertion causing a frameshift that disrupts helix 12 of the TRα1 ligand-binding domain, abolishing T3 binding and coactivator recruitment while preserving (indeed enhancing) corepressor binding — producing a potent dominant-negative receptor closely analogous to human disease-causing truncating variants. - Phenotype recapitulation: Near-normal standard thyroid function tests (mirroring the human diagnostic challenge), growth retardation, delayed bone development, reduced fat mass and liver size, abnormal (grossly abnormal) bone morphology with paradoxically preserved/high bone mass and normal bone strength in adult females, short stature, and short limbs — closely recapitulating the human skeletal phenotype. - Erythroid phenotype: Thra1^PV/+ mice show abnormal red blood cell indices similar to patients, with decreased expression of the erythroid master regulator Gata-1 and its target genes in bone marrow, proposed as the mechanism by which mutant TRα1PV impairs erythropoiesis (mouse-model mechanistic claim — note this Gata1-repression mechanism was not corroborated in the human erythroid-progenitor study by van Gucht et al. 2017, which instead emphasized a proliferation/differentiation-balance defect without mention of GATA1 — a human/model divergence worth flagging when curating the erythropoiesis mechanism). - Corepressor rescue experiment: Introducing a mutation in NCoR1 that abrogates its interaction with TR, in the Thra1^PV/+ background, ameliorates growth and bone-development phenotypic abnormalities — direct genetic evidence for the corepressor-centered dominant-negative mechanism. - Pharmacologic rescue (HDAC inhibition): Conflicting results between two independent studies (Subramanian 2014 positive; Freudenthal 2019 negative for skeletal endpoints specifically) — see Section 12 for detail on this model divergence. - Behavioral/CNS models: Neuronal-specific expression of a dominant-negative TRα mutant alters mouse behavior (anxiety/depressive-like behaviors noted); relevant to the human neurocognitive/psychiatric phenotype but an extrapolation from a targeted-expression model rather than the global knock-in. - Gonadal expression models: Expression of dominant-negative TRα1 in Leydig and Sertoli cells demonstrated no additional reproductive defect compared with Sertoli-cell-only expression, suggesting TRα1 dysfunction in Leydig cells does not compound the male reproductive phenotype beyond the Sertoli-cell effect — consistent with the clinical observation that fertility is largely preserved in human RTHα. - Limitations of the mouse model: No fully "amendable" (i.e., easily genetically/embryologically manipulable) mouse model exists for studying very early embryonic/developmental consequences of TRα1 dominant-negative mutations — this gap motivated development of the zebrafish models below.

Zebrafish models: - CRISPR/Cas9-generated dominant-negative mutations in the duplicated zebrafish thra paralogs (thraa, thrab) allow study of THRA variant consequences during early embryonic development, which is experimentally inaccessible in mammalian models. - Human THRA variants have been functionally tested in vivo by expression in zebrafish, demonstrating "in vivo functional consequences of human THRA variants" and validating zebrafish as a variant-classification/functional-assay platform. - A specific thraa mutant line carrying an 8-bp insertion (truncating Thraa, impairing TH signaling) has been separately characterized for its effect on cardiac regeneration, finding that thraa loss-of-function enhances zebrafish heart regenerative capacity through metabolic/hypoxic regulation — an intriguing but mechanistically distinct line of investigation (cardiac regeneration biology) rather than a direct RTHα disease model, and should not be conflated with the human cardiac hypothyroid phenotype (bradycardia/reduced contractility) without further validation. - THRA mutant zebrafish also show heart defects, directly supporting a TRα-dependent cardiac developmental role relevant to human cardiac findings.

Cellular/in vitro models: - Patient-derived human erythroid progenitor cells (HEPs) cultured from peripheral blood of RTHα patients — used to directly demonstrate the human erythropoiesis defect (van Gucht 2017), representing a direct human cellular model rather than an animal surrogate. - Reporter-gene transactivation assays (transfected cell lines expressing mutant TRα1/TRα2 constructs) — the standard functional-characterization approach for essentially every novel missense variant reported (e.g., A263V, N359Y, R384C functional studies cited above).

Resources: MGI (mouse Thra models), ZFIN (zebrafish thraa/thrab lines); no dedicated IMPC/KOMP conditional RTHα allele set was identified in this pass beyond the PV knock-in lineage.

Summary of Key Evidence Gaps (for curation awareness)

Precise per-variant gnomAD/ClinVar allele-frequency and ACMG classification detail was not individually verified for every reported variant in this pass and should be confirmed directly against ClinVar/gnomAD before binding specific variant records.
The erythropoiesis mechanism shows a model-organism/human divergence: mouse data implicate Gata1 repression; the direct human progenitor-cell study instead emphasizes a proliferation/differentiation kinetic defect without invoking Gata1 — this is a genuine discrepancy, not merely a gap, and should be modeled as such (e.g., via divergences/HUMAN_MODEL_MISMATCH framing) rather than harmonized.
The HDAC-inhibitor (SAHA) therapeutic strategy has directly conflicting preclinical results (positive in Subramanian 2014; negative on skeletal endpoints in Freudenthal 2019) and should not be curated as a settled positive therapeutic lead.
Exact PMIDs for the JCRPE clinical-spectrum review and the J Endocr Soc untreated-adult cohort paper were not definitively captured during this search pass (PMC identifiers were obtained; PMID lookup should be completed at curation time).
The DEEPTYPE registry (NCT06566066) protocol detail (explicit RTHα inclusion, sponsor) could not be retrieved and should be verified directly on ClinicalTrials.gov.

Sources

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	20
Resolved	20
Unresolved (possible confabulation)	0
Unverifiable	0
References weighed for topical relevance	20
On topic	18
Off topic	0

All extracted references resolved successfully.

Term Validation

Checked with linkml-term-validator 0.4.5, through the ols: adapter.

Outcome	Count
Terms checked	48
Resolved	44
Unresolved (possible confabulation)	1
Obsolete	1
Unverifiable	2
Terms whose name was checked	41
Terms named correctly	32
Terms named as a different term	6
Terms whose name is worth a second look	3

Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

HP:0010701 (1 mention) - the report calls it "Skin tags"; HP calls it Abnormal circulating immunoglobulin concentration
HP:0001923 (1 mention) - the report calls it "Normocytic anemia"; HP calls it Reticulocytosis
GO:0004887 (3 mentions) - the report calls it "thyroid hormone receptor activity"; GO calls it GO_0004887
GO:0007416 (1 mention) - the report calls it "synapse assembly, for GABAergic interneuron defect"; GO calls it synapse assembly
CL:0000216 (1 mention) - the report calls it "Sertoli cell — relevant to gonadal expression studies"; CL calls it Sertoli cell
UBERON:0001968 (1 mention) - the report calls it "skeletal system"; UBERON calls it semen

Unresolved terms

These identifiers do not exist in an ontology that resolved other terms from the same prefix, so they were most likely invented:

HP:0008977 (1 mention) - HP does not contain this term

Obsolete terms

These terms are real but deprecated. Citing one is not a fabrication; it does mean the report is naming something the ontology has retired:

GO:0004887 (GO_0004887) (3 mentions) - replaced by GO:0004879

Terms whose name is worth a second look

The report's name for these is recognisably related to the term's own name without being one of them. A loose paraphrase reads the same way as a citation of the wrong sibling term - and so does a related synonym, which the ontology records precisely because it names something adjacent rather than the same thing - so these are listed rather than judged:

GO:0006355 (2 mentions) - the report calls it "regulation of DNA-templated transcription", "regulation of transcription"; GO calls it regulation of DNA-templated transcription
CL:0000617 (1 mention) - the report calls it "GABAergic interneuron"; CL calls it GABAergic neuron
CL:0000187 (1 mention) - the report calls it "myocyte"; CL calls it muscle cell, and lists "myocyte" among its other names

Terms named inconsistently

The report gives these identifiers more than one name of its own:

GO:0006355 - called "regulation of DNA-templated transcription", "regulation of transcription"

Prefixes with no resolver

Terms carrying these prefixes were not checked either way, because no configured ontology covers them. An unrecognised prefix may name an ontology this run could not reach as easily as one that does not exist, so nothing here is evidence of fabrication: MGI.

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Classifications

Mappings

Definitions

Inheritance

Discussions and Knowledge Gaps

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Biochemical Markers

Progression

Prevalence

Differential Diagnoses

Experimental Models

Animal Models

Source YAML

References & Deep Research

References

Deep Research

Resistance to Thyroid Hormone Alpha (RTHα) — Comprehensive Research Report

1. Disease Information

2. Etiology

3. Phenotypes

Neurodevelopmental / Behavioral

Growth / Skeletal

Gastrointestinal

Dermatologic

Hematologic

Cardiovascular / Metabolic

Laboratory abnormalities

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

Ordered causal chain

Molecular pathways

Cellular processes

Protein dysfunction

Biochemical abnormalities

Molecular profiling / advanced technologies

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome/Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Summary of Key Evidence Gaps (for curation awareness)

Sources

Reference Validation

Term Validation

Terms the report names something else

Unresolved terms

Obsolete terms

Terms whose name is worth a second look

Terms named inconsistently

Prefixes with no resolver