Isolated Growth Hormone Deficiency

Endocrine MONDO:0000050 Pathograph 16 Show in embeddings browser Growth Hormone Deficiency

Deficient pituitary growth hormone (GH) secretion in the absence of other anterior pituitary hormone deficiencies, producing proportionate short stature with normal body proportions and delayed bone age. Root umbrella entry over four Mendelian molecular-cause subtypes distinguished by mode of inheritance and by whether GH is completely absent or merely diminished: type IA (autosomal recessive, complete absence of endogenous GH from a severe GH1 loss-of-function lesion - curated at entity level as its own dismech entry and cross-referenced here), type IB (autosomal recessive, low but detectable GH, most often from a GHRHR loss-of-function variant and less often an intrinsic GH1 defect), type II (autosomal dominant, a GH1 intron-3 splice-site or splicing-enhancer variant that produces a dominant-negative 17.5-kDa GH isoform), and type III (X-linked, associated with the BTK region at Xq21.3-q22 or, in a separate route, with SOX3 dosage at Xq26-27). Distinct from Growth_Hormone_Insensitivity_Syndrome (Laron syndrome and its molecular relatives), where GH secretion is normal or elevated but the receptor or a post-receptor signal is defective. Here the receptor is intact and it is the ligand itself - or, for type IB/III, the somatotroph's ability to make and release it - that is deficient. This is also why recombinant GH replacement is generally effective in types IB, II, and III, unlike in type IA, where treatment failure from anti-GH antibody formation is part of the disease itself (see the type IA entry).

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Inheritance

Autosomal recessive (types IA, IB) HP:0000007

Applies to type IA (curated separately) and type IB, both requiring biallelic loss of function at GH1 or, for type IB, most often GHRHR.

Autosomal recessive inheritance

Show evidence (1 reference)

PMID:12207163 SUPPORT Human Clinical

"Two forms are autosomal recessively (IGHD type IA and IB), one is autosomal dominantly (IGHD type II) and one X-linked inherited."

States the inheritance pattern for all four subtypes in one sentence.

Autosomal dominant (type II) HP:0000006

A single heterozygous GH1 splice-affecting variant is sufficient, because the resulting 17.5-kDa isoform acts as a dominant negative against the normal protein produced by the other allele.

Autosomal dominant inheritance

Show evidence (1 reference)

PMID:12720086 SUPPORT Human Clinical

"Isolated growth hormone deficiency type II (IGHD II) is characterized by short stature due to dominant-negative mutations of the human growth hormone gene (GH1)."

States the dominant-negative, autosomal dominant basis of type II.

X-linked recessive (type III) HP:0001419

Applies to the BTK-region (Fleisher syndrome) route, in which affected hemizygous males have both agammaglobulinemia and GH deficiency.

X-linked recessive inheritance

Show evidence (1 reference)

PMID:7650402 SUPPORT Human Clinical

"In 1980 the clinical syndrome of X-linked hypogammaglobulinemia and isolated growth hormone deficiency (XLA/GHD) was described."

The clinical description this X-linked pattern is drawn from.

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Subtypes

Type IA (GH1 severe loss-of-function; complete GH absence) MONDO:0009876

GH1 hgnc:4261 Autosomal recessive inheritance

The most severe Mendelian form: autosomal recessive, complete absence of endogenous GH from a severe GH1 loss-of-function lesion (most often a 6.7-45 kb deletion, also frameshift and nonsense variants), with a distinctive treatment-failure mechanism (anti-GH antibody formation on replacement, because the immune system was never exposed to the hormone). Curated at entity level in kb/disorders/Isolated_Growth_Hormone_Deficiency_Type_IA.yaml (MONDO:0009876); it is cross-referenced here and not duplicated.

Show evidence (1 reference)

PMID:12207163 SUPPORT Human Clinical

"Two forms are autosomal recessively (IGHD type IA and IB), one is autosomal dominantly (IGHD type II) and one X-linked inherited."

Places type IA within the four-way classification this root entry models, alongside the other three subtypes below.

Type IB (GHRHR or GH1 partial loss-of-function; diminished but detectable GH) MONDO:0013006

GHRHR hgnc:4266 GH1 hgnc:4261 Autosomal recessive inheritance

Autosomal recessive, with low but detectable GH (unlike type IA's complete absence), significantly retarded bone age, and - because some endogenous GH was always present - a positive growth response and immunologic tolerance to exogenous GH therapy. The best-characterized molecular cause is an inactivating mutation of the GH-releasing hormone receptor (GHRHR), which leaves somatotrophs present but unable to receive the hypothalamic signal that drives GH synthesis and secretion; the founding description is "Dwarfism of Sindh," a consanguineous Pakistani kindred with a GHRHR nonsense mutation. An intrinsic GH1 defect is a much rarer alternative cause: a systematic sequencing survey found GH1 alterations in only 1.7% of subjects with the type IB phenotype, versus two-thirds of type IA families, and concluded that most type IB cases are not explained by GH1 itself.

Show evidence (2 references)

PMID:9814493 SUPPORT Human Clinical

"DNA sequencing revealed a nonsense mutation (Glu50-->Stop) in the extracellular domain of the GHRH-R."

The founding molecular description of GHRHR-caused type IB, in a consanguineous Pakistani kindred (dwarfism of Sindh).

PMID:9432120 SUPPORT Human Clinical

"the low frequency rate of 1.7% (2/119) of GH-1 gene mutations responsible for the most common phenotype of IGHD, namely type IB"

Quantifies how rarely GH1 itself, rather than GHRHR or another candidate gene, explains the type IB phenotype.

Type II (autosomal dominant GH1 intron-3 splice variant; dominant-negative 17.5-kDa isoform) MONDO:0008250

GH1 hgnc:4261 Autosomal dominant inheritance

Autosomal dominant, and the mechanistically richest subtype: a heterozygous variant at the GH1 intron-3 splice donor site (the recurrent "hot spot" IVS3+1G>A is the most frequently reported single lesion) or at a nearby exonic splicing enhancer causes skipping of exon 3, producing a truncated, dominant-negative 17.5-kDa GH isoform alongside normal 22-kDa GH from the other allele. The 17.5-kDa isoform disrupts GH secretory granules in a dose-dependent manner and separately triggers endoplasmic reticulum stress and caspase-mediated apoptosis in somatotrophs, destroying most of them in transgenic mouse models and causing anterior pituitary hypoplasia. Clinical severity is variable even among carriers of the same mutation, which splicing-enhancer-strength studies suggest may reflect how much 17.5-kDa isoform a given variant actually produces.

Show evidence (2 references)

PMID:17073157 SUPPORT Human Clinical

"The "hot spot" of mutations is 5'-donor splicing site of GH-1 intron 3, while IVS3 +IG>A mutation can be regarded as the most incident in type II isolated growth hormone deficiency in the Russian population."

Identifies the recurrent intron-3 donor-site hot spot underlying most type II cases in this cohort.

PMID:12720086 SUPPORT Human Clinical

"Isolated growth hormone deficiency type II (IGHD II) is characterized by short stature due to dominant-negative mutations of the human growth hormone gene (GH1)."

Establishes the dominant-negative GH1 mechanism that defines this subtype, elaborated in the pathophysiology section below.

Type III (X-linked; BTK-region or SOX3) MONDO:0010615

BTK hgnc:1133 SOX3 hgnc:11199 X-linked recessive inheritance

X-linked. The classic description (Fleisher syndrome) is a contiguous phenotype of X-linked hypogammaglobulinemia and isolated GH deficiency (XLA/GHD) mapping near the BTK gene at Xq21.3-q22, the same locus disrupted in Bruton's X-linked agammaglobulinemia (kb/disorders/X-linked_Agammaglobulinemia.yaml). The molecular basis of the GHD component is genuinely unresolved: in the kindred where it was originally described, BTK mRNA and protein were present at normal levels and the BTK coding sequence was normal, showing that XLA/GHD is not simply Bruton's XLA with an incidental growth phenotype, and a contiguous-deletion mechanism was explicitly excluded in three further XLA/GHD patients. A separate X-linked route is dosage alteration (duplication or deletion) of SOX3 at Xq26-27, which more typically produces infundibular hypoplasia with combined pituitary hormone deficiency rather than a strictly isolated GH deficit, though isolated GH deficiency has been reported as part of its phenotypic spectrum.

Show evidence (2 references)

PMID:7650402 SUPPORT Human Clinical

"In 1980 the clinical syndrome of X-linked hypogammaglobulinemia and isolated growth hormone deficiency (XLA/GHD) was described."

Establishes the contiguous XLA/GHD phenotype this subtype is named for, distinct from Bruton's XLA alone.

PMID:15800844 SUPPORT Human Clinical

"We conclude that both over- and underdosage of SOX3 are associated with similar phenotypes, consisting of infundibular hypoplasia and hypopituitarism but not necessarily MR."

Establishes SOX3 dosage as a second, molecularly distinct X-linked route into this subtype's phenotype.

Discussions and Knowledge Gaps

What is the actual genetic lesion responsible for the growth hormone deficiency component of X-linked hypogammaglobulinemia and isolated growth hormone deficiency (XLA/GHD, "Fleisher syndrome"), if it is not BTK itself?

KNOWLEDGE GAP OPEN gap_type3_btk_mechanism_unknown

Attached to

pathophysiology#BTK-Region Xq21.3-q22 Genetic Lesion genetic#BTK

The clinical entity is well established and clearly X-linked, but the two molecular studies available on the founding kindred and a further three XLA/GHD patients both point away from BTK as the GHD-causing gene: BTK mRNA, protein, and coding sequence were normal in the original patient, and a contiguous deletion spanning the flanking region was explicitly excluded in three more patients. Type III is therefore curated with BTK as a RISK_FACTOR / locus marker rather than a CAUSATIVE gene for the GHD arm specifically, and the causal_link_type on this node's downstream edge is INDIRECT_UNKNOWN_INTERMEDIATES rather than DIRECT. No later molecular candidate for the actual GHD gene at this locus was found in the literature searched for this entry.

Proposed experiments

Whole-genome sequencing and fine mapping of remaining XLA/GHD kindreds

xla_ghd_locus_fine_mapping

Apply modern long-read sequencing and RNA-seq to XLA/GHD families (rather than the Southern-blot and cDNA-clone methods available at the time of the founding studies) to identify structural variants, regulatory-region lesions, or a second gene at Xq21.3-q22 that segregates with the GHD component independent of BTK status.

Show evidence (1 reference)

PMID:7650402 SUPPORT Human Clinical

"These results suggest that undescribed genes critical for B cell development and growth hormone production exist on the X chromosome."

The original authors' own framing of the open question, over two decades before this entry was curated.

Does the anterior pituitary hypoplasia and majority somatotroph loss seen in transgenic mice overexpressing the dominant-negative 17.5-kDa GH isoform actually occur to the same degree in human type II patients, or is the human disease driven predominantly by the (also demonstrated) secretory-granule-disruption arm without comparable cell loss?

HUMAN MODEL MISMATCH OPEN gap_type2_mouse_pituitary_hypoplasia_human_extrapolation

Attached to

pathophysiology#Anterior Pituitary Somatotroph Loss

The somatotroph-destruction and pituitary-hypoplasia finding comes from a transgenic mouse model overexpressing the isoform, not from pituitary histology or imaging in human type II patients, who are diagnosed and followed clinically and biochemically rather than by pituitary biopsy. Mouse overexpression systems can produce isoform levels and expression patterns that do not match the heterozygous dosage in human patients (one mutant allele plus one normal allele, rather than an overexpression transgene), so the degree of somatotroph loss - as opposed to reversible secretory dysfunction - in human disease is not established by this evidence alone.

Proposed experiments

Pituitary MRI volumetry in molecularly confirmed type II patients

type2_pituitary_mri_volumetry

Compare anterior pituitary volume by MRI between type II patients (stratified by the specific GH1 variant and its reported splicing-enhancer strength) and type IB/unaffected relatives, to test whether structural pituitary hypoplasia is present in humans and whether it scales with predicted 17.5-kDa isoform dose as the mouse and cell data suggest.

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Pathophysiology

GHRHR or GH1 Partial Loss-of-Function Variant

Most commonly a biallelic inactivating GHRHR variant (the founding description is a nonsense mutation, Glu50Stop, in the receptor's extracellular domain, in a consanguineous Pakistani kindred); much less commonly an intrinsic GH1 variant, which a systematic sequencing survey found in only 1.7% of type IB subjects. Both converge on the same clinical picture - low but detectable GH, unlike type IA's complete absence.

Genetic context GHRHR hgnc:4266 variant_origin: GERMLINE zygosity: HOMOZYGOUS functional_impact_category: LOSS_OF_FUNCTION

Modeled on the GHRHR route, the better-characterized of the two genetic causes; a rarer intrinsic GH1 defect can produce the same downstream state by a distinct mechanism not captured by this genetic_context block.

growth hormone-releasing hormone receptor activity GO:0016520 ⇓ LOSS OF FUNCTION

Downstream

Reduced Somatotroph Growth Hormone Synthesis and Secretion Loss of GHRH receptor signalling removes the hypothalamic drive for GH synthesis and secretion by intact somatotrophs; a GH1 defect acts more directly on the hormone itself. Either way the result is reduced, not absent, GH.

Show evidence (2 references)

PMID:9814493 SUPPORT Human Clinical

"DNA sequencing revealed a nonsense mutation (Glu50-->Stop) in the extracellular domain of the GHRH-R."

The variant defining the GHRHR route into this node.

PMID:9432120 SUPPORT Human Clinical

"the low frequency rate of 1.7% (2/119) of GH-1 gene mutations responsible for the most common phenotype of IGHD, namely type IB"

Quantifies the much rarer GH1 route bundled into this same trigger node.

Reduced Somatotroph Growth Hormone Synthesis and Secretion

Somatotrophs are present and capable of secretion, unlike the somatotroph loss modeled for type II below; without the GHRH signal (or with an intrinsic GH1 defect) they simply make and release less hormone.

Somatotroph CL:0002312

growth hormone secretion GO:0030252 ↓ DECREASED

Downstream

Insufficient Circulating Growth Hormone

Show evidence (1 reference)

PMID:9814493 SUPPORT Human Clinical

"Serum GH did not respond to provocative stimuli (GHRH, L-dopa, or clonidine)."

Documents the functional consequence of GHRHR loss on somatotroph GH output in the founding kindred.

GH1 Intron-3 Splice-Site or Splicing-Enhancer Variant

A single mutant GH1 allele produces a mixture of normal transcript and an aberrantly spliced transcript lacking exon 3, while the other allele continues to produce normal transcript - the genetic basis of the dominant-negative phenotype elaborated in the nodes below.

Genetic context GH1 hgnc:4261 variant_origin: GERMLINE zygosity: HETEROZYGOUS functional_impact_category: DOMINANT_NEGATIVE

Most frequently the recurrent intron-3 donor splice-site variant IVS3+1G>A; other reported lesions weaken exon-3 splicing enhancers (dual enhancers are normally required for exon-3 definition) rather than disrupting the canonical splice site itself.

Downstream

Exon 3 Skipping and Dominant-Negative 17.5-kDa GH Isoform Production

Show evidence (2 references)

PMID:17073157 SUPPORT Human Clinical

Identifies the recurrent hot-spot variant modeled on this node.

PMID:12720086 SUPPORT In Vitro

"We demonstrate that dual splicing enhancers are required to ensure exon 3 definition to produce full-length 22-kDa hormone."

Establishes the splicing-enhancer route into exon-3 skipping, distinct from a canonical splice-site variant but converging on the same downstream isoform. This is an in-vitro splicing-reporter finding, not a clinical observation.

Exon 3 Skipping and Dominant-Negative 17.5-kDa GH Isoform Production

The mutant allele's transcript skips exon 3, yielding a 17.5-kDa GH isoform lacking the residues exon 3 would have encoded (also described as del32-71 GH), co-expressed with normal 22-kDa GH from the wild-type allele. This isoform is not simply inactive - it actively interferes with the wild-type hormone's normal secretion, which is what makes the variant dominant-negative rather than a simple loss-of-function allele. Splicing-enhancer variants that only partially weaken exon-3 recognition produce variable amounts of the 17.5-kDa isoform, offering a candidate explanation for the clinical variability seen among type II patients.

Downstream

Disruption of GH Secretory Granules

Endoplasmic Reticulum Stress and Somatotroph Apoptosis

Show evidence (2 references)

PMID:12720086 SUPPORT In Vitro

"mutations that cause exon 3 skipping and produce a dominant-negative 17.5-kDa isoform in humans also cause a dose-dependent disruption of GH secretory vesicles when expressed in GC cells"

Names the 17.5-kDa isoform and its dose-dependent effect on secretory vesicles, the basis for the two downstream consequence nodes below. Quote trimmed to the GC-cell (IN_VITRO) clause; the same source sentence continues "...and transgenic mice," and that in-vivo corroboration is evidenced separately, as MODEL_ORGANISM, on the downstream "Anterior Pituitary Somatotroph Loss" node below.

PMID:23736291 SUPPORT In Vitro

"An exon 3 deletion in GH (del32-71 GH) is produced from a mutant allele, whereas wild-type GH is produced from the other allele. Several studies have demonstrated a dominant negative effect of del32-71 GH on wild-type GH secretion"

Confirms the same isoform under an alternative name (del32-71 GH) and its dominant-negative effect on the co-expressed wild-type hormone.

Disruption of GH Secretory Granules

Expression of the 17.5-kDa isoform causes a dose-dependent disruption of GH secretory vesicles, directly impairing regulated release of the co-packaged normal hormone independent of the apoptotic arm below.

growth hormone secretion GO:0030252 ↓ DECREASED

secretory granule GO:0030141

Downstream

Insufficient Circulating Growth Hormone

Show evidence (1 reference)

PMID:12720086 SUPPORT In Vitro

"mutations that cause exon 3 skipping and produce a dominant-negative 17.5-kDa isoform in humans also cause a dose-dependent disruption of GH secretory vesicles when expressed in GC cells"

Direct evidence for the secretory-granule-disruption arm, observed in the GC cell line. The same source sentence also reports this in transgenic mice; that arm is evidenced separately, as MODEL_ORGANISM, on the "Anterior Pituitary Somatotroph Loss" node below rather than forced onto this quote.

Endoplasmic Reticulum Stress and Somatotroph Apoptosis

Unfolded 17.5-kDa isoform accumulates in the endoplasmic reticulum and activates all three canonical ER stress-response arms (PERK, ATF6, and IRE1), with downstream caspase-3/7 activation and, in a subset of cell models, DNA fragmentation - a second, apoptotic route to reduced GH output that is independent of the granule-disruption arm above. Overexpressing the IRE1-downstream transcription factor XBP1(S) reversed the caspase activation in this system, identifying IRE1 signalling as load-bearing for the apoptotic effect rather than merely correlated with it.

Somatotroph CL:0002312

intrinsic apoptotic signaling pathway in response to endoplasmic reticulum stress GO:0070059 ↑ INCREASED

Downstream

Anterior Pituitary Somatotroph Loss

Show evidence (2 references)

PMID:23736291 SUPPORT In Vitro

"del32-71 GH induction decreased cell viability, increased expression of 3 major ER stress response pathways"

Direct evidence for the ER-stress/apoptosis arm in a doxycycline-controlled cell model of the dominant-negative isoform. The three pathways named in the description (PERK, ATF6, IRE1) are the same sentence's parenthetical continuation in the source abstract.

PMID:23736291 SUPPORT In Vitro

"overexpression of XBP1(S), a nuclear transcription factor downstream of IRE1, completely reversed the observed caspase activation"

Shows IRE1/XBP1(S) signalling is mechanistically load-bearing for the apoptotic effect, not just co-occurring with it.

Anterior Pituitary Somatotroph Loss

In transgenic mice, overexpression of the dominant-negative 17.5-kDa isoform destroyed the majority of somatotrophs and produced anterior pituitary hypoplasia. This structural consequence has been demonstrated in the mouse model rather than directly imaged in human type II patients; see the discussion below.

Downstream

Insufficient Circulating Growth Hormone

Show evidence (1 reference)

PMID:12720086 SUPPORT Model Organism

"overexpression of the dominant-negative 17.5-kDa isoform also destroys the majority of somatotrophs, leading to anterior pituitary hypoplasia in transgenic mice."

The transgenic mouse evidence for somatotroph destruction and resulting pituitary hypoplasia.

BTK-Region Xq21.3-q22 Genetic Lesion

Named for the BTK locus because that is the established cause of the co-occurring agammaglobulinemia (Bruton's X-linked agammaglobulinemia, kb/disorders/X-linked_Agammaglobulinemia.yaml), not because BTK itself has been shown to cause the GH deficiency.

Genetic context BTK hgnc:1133 variant_origin: GERMLINE

X-linked segregation of GH deficiency together with agammaglobulinemia is well established clinically in this region, but the specific genetic lesion responsible for the GHD component has not been identified: in the originally described kindred BTK mRNA and protein were both present at normal levels and the BTK coding sequence was normal, and a contiguous deletion spanning the region was explicitly excluded in three further XLA/GHD patients. This is a genuine knowledge gap (see discussions below), not a settled BTK mechanism.

Downstream

Insufficient Circulating Growth Hormone The intermediate cellular mechanism connecting this X-linked locus to reduced somatotroph GH output is unknown; only the clinical segregation and the anatomic locus are established.

Show evidence (2 references)

PMID:7650402 SUPPORT Human Clinical

"BTK mRNA was normal in size and abundance, and the mRNA sequence was normal over the coding region, except for a single silent mutation. BTK protein was present in normal amounts in PBMC of this patient. Thus, at the molecular level, XLA/GHD is a different disease entity from Bruton's XLA."

PARTIAL: it establishes the X-linked locus and the clinical entity but actively refutes BTK itself as the GHD-causing gene in this patient, which is exactly the mechanistic gap this node records.

PMID:7959728 SUPPORT Human Clinical

"Southern blot analysis using cDNA clones isolated from this region permitted us to exclude a contiguous deletion syndrome as an underlying defect in three patients with XLA and associated growth hormone deficiency."

PARTIAL: rules out the most obvious structural explanation (contiguous deletion) without identifying an alternative.

SOX3 Dosage Alteration

A molecularly distinct second route into the X-linked subtype, acting through hypothalamic-pituitary developmental patterning rather than through a locus linked to agammaglobulinemia.

Genetic context SOX3 hgnc:11199

Duplication or deletion of the dosage-sensitive transcription factor SOX3 at Xq26-27; either direction of dosage change has been reported with infundibular hypoplasia and hypopituitarism, more typically combined pituitary hormone deficiency rather than a strictly isolated GH deficit.

Downstream

Insufficient Circulating Growth Hormone Acts via disrupted hypothalamic-pituitary axis development (infundibular hypoplasia); the isolated-GHD presentation is part of a broader spectrum that more often includes other pituitary hormone deficiencies.

Show evidence (1 reference)

PMID:15800844 SUPPORT Human Clinical

"We conclude that both over- and underdosage of SOX3 are associated with similar phenotypes, consisting of infundibular hypoplasia and hypopituitarism but not necessarily MR."

The dosage-sensitivity finding this node is built on.

Insufficient Circulating Growth Hormone

The convergent state shared by types IB, II, and III: circulating GH is reduced by disruption of its synthesis, secretion, or the somatotroph population producing it - in contrast to type IA, where the GH1 gene product is absent altogether (curated separately). The route into this state differs by subtype (see the arms above), but the downstream consequence for growth is the same.

Downstream

Loss of Growth Hormone Receptor Signalling

Show evidence (1 reference)

PMID:17965963 SUPPORT Human Clinical

"In a small number of children with IGHD, defects in the GH, GH-releasing hormone receptor (GHRH-R), and GH1 genes have been identified."

Ties the distinct genetic triggers modeled above to the shared downstream state of GH insufficiency.

Loss of Growth Hormone Receptor Signalling

With less ligand available, growth hormone receptor signalling in peripheral target tissues (chiefly liver, driving IGF-1 generation) is correspondingly reduced. The receptor itself is normal throughout this entry, which is what distinguishes it mechanistically from Growth_Hormone_Insensitivity_Syndrome.

growth hormone receptor signaling pathway GO:0060396 ↓ DECREASED

Downstream

Impaired Longitudinal Growth

Show evidence (1 reference)

PMID:9814493 SUPPORT Human Clinical

"Insulin-like growth factor I (IGF-I) and IGF-binding protein 3 were low (5.2 +/- 2.0 ng/mL and 0.42 +/- 0.13 microg/mL, respectively; mean +/- SD) but rose normally with GH treatment."

IGF-1/IGFBP-3 are the direct downstream readout of GH receptor signalling in the liver. Low IGF-1 in the untreated (ligand-deficient) state, rising normally once ligand is supplied, is direct evidence that receptor signalling tracks GH availability rather than being intrinsically impaired - exactly the claim this node makes.

Impaired Longitudinal Growth

Reduced GH-dependent IGF-1 generation slows linear growth, producing proportionate short stature with delayed skeletal maturation - milder and later-declaring than type IA's universal severe dwarfism by six months, consistent with GH being reduced rather than absent.

Downstream

Short Stature

Delayed Skeletal Maturation

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Pathograph

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

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Phenotypes

Digestive 1

Prolonged Neonatal Jaundice HP:0006579

Show evidence (1 reference)

PMID:9802480 SUPPORT Human Clinical

"Breech delivery, neonatal hypoglycemia, jaundice, micropenis, or single central incisor occurred equally with both isolated GHD and MPHD."

Same source and same "occurred equally" statement as the neonatal hypoglycemia phenotype above, applied to jaundice.

Endocrine 1

Anterior Pituitary Hypoplasia HP:0010627

Show evidence (1 reference)

PMID:9802480 SUPPORT Human Clinical

"Pituitary abnormalities were common in both groups (80% with isolated GHD, 93% with MPHD)."

Directly quantifies the pituitary-imaging abnormality rate in isolated GHD specifically (not just the combined-deficiency comparator group), from a 35-patient MRI series.

Genitourinary 1

Micropenis HP:0000054

Show evidence (1 reference)

PMID:9802480 SUPPORT Human Clinical

"Breech delivery, neonatal hypoglycemia, jaundice, micropenis, or single central incisor occurred equally with both isolated GHD and MPHD."

Same source and same "occurred equally" statement, applied to micropenis; a separate, larger GH-registry study (PMID:15198294) found micropenis in 55/100 hypoglycemic males but in a cohort that was mostly combined pituitary hormone deficiency (148/169) rather than isolated GHD (12/169), so it is cited here only as corroboration, not as the primary support.

Musculoskeletal 1

Delayed Skeletal Maturation HP:0002750

Show evidence (1 reference)

PMID:36960394 SUPPORT Human Clinical

"Patients with IGHD type IV (IGHD4) have a short stature, reduced serum GH levels, and delayed bone age."

A direct statement of delayed bone age in a closely related, GHRHR-caused IGHD entity (type IV, out of this entry's declared scope - see notes). No cached source among the type IB/II/III literature actually screened for this entry (PMID:9814493, PMID:9432120, PMID:10678654, PMID:8528260, PMID:8288694) supplies a quotable bone-age sentence, despite MONDO's own def: text for type IB asserting "significantly retarded bone age." This quote is the closest verifiable substitute rather than a direct type IB/II/III finding, and the gap is recorded rather than papered over.

Growth 1

Short Stature VERY_FREQUENT HP:0004322

Show evidence (1 reference)

PMID:9814493 SUPPORT Human Clinical

"Mean height was 7.2 SD below the norm, with mean adult heights of 130 cm for males and 113.5 cm for females."

Quantifies the severity of short stature in a GHRHR-null (type IB) cohort.

Other 2

Reduced Circulating Growth Hormone Concentration HP:0034323

Show evidence (1 reference)

PMID:9814493 SUPPORT Human Clinical

"Serum GH did not respond to provocative stimuli (GHRH, L-dopa, or clonidine)."

Documents blunted GH secretion in the type IB (GHRHR-null) cohort.

Neonatal Hypoglycemia HP:0001998

Show evidence (1 reference)

PMID:9802480 SUPPORT Human Clinical

"Breech delivery, neonatal hypoglycemia, jaundice, micropenis, or single central incisor occurred equally with both isolated GHD and MPHD."

States explicitly that neonatal hypoglycemia occurs in isolated GHD at a rate statistically indistinguishable from the combined-deficiency comparator group, i.e., it is not an artifact of pooling with MPHD cases.

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Genetic Associations

GH1 (The gene most often implicated across this entry's subtypes: severe loss-of-function lesions cause type IA (curated separately), rare intrinsic variants are an uncommon cause of type IB, and heterozygous intron-3 splice or splicing-enhancer variants producing a dominant-negative 17.5-kDa isoform cause type II.)

Gene: GH1 hgnc:4261 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:9432120 SUPPORT Human Clinical

"Familial isolated growth hormone deficiency (IGHD) is associated with at least four Mendelian disorders. These include two forms that have autosomal recessive inheritance (IGHD types IA and IB) as well as autosomal dominant (IGHD type II) and X-linked (IGHD III) forms."

The four-way classification GH1 (and the other genes below) sit within.

GHRHR (Biallelic inactivating variants cause type IB; the founding description is a homozygous nonsense mutation (Glu50Stop) in a consanguineous Pakistani kindred ("Dwarfism of Sindh"), later shown to be shared by other affected families.)

Gene: GHRHR hgnc:4266 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:9814493 SUPPORT Human Clinical

"This mutation predicts a severely truncated GHRH-R; it is identical to that recently reported in four patients from two other families."

Shows the founding variant recurs across independent families rather than being a single private mutation.

BTK (The gene disrupted in the well-established co-occurring agammaglobulinemia at this X-linked locus. Curated as RISK_FACTOR rather than CAUSATIVE for the GH-deficiency component specifically, because BTK coding sequence and protein were normal in the originally described XLA/GHD kindred and a contiguous deletion was excluded in three further patients - the GHD-causing element at this locus has not been identified (see discussions below).)

Gene: BTK hgnc:1133 relationship_type: RISK_FACTOR

Show evidence (1 reference)

PMID:7650402 SUPPORT Human Clinical

"Thus, at the molecular level, XLA/GHD is a different disease entity from Bruton's XLA."

PARTIAL: supports the X-linked locus and clinical entity while refuting BTK itself as the causal gene for the GHD component.

SOX3 (Dosage alteration (duplication or deletion) at Xq26-27 causes a second, molecularly distinct X-linked route into this subtype, more often presenting as combined pituitary hormone deficiency with infundibular hypoplasia than as isolated GH deficiency.)

Gene: SOX3 hgnc:11199 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:15800844 SUPPORT Human Clinical

"We conclude that both over- and underdosage of SOX3 are associated with similar phenotypes, consisting of infundibular hypoplasia and hypopituitarism but not necessarily MR."

The dosage-sensitivity finding underlying this gene's inclusion.

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Medical Actions

Recombinant Human Growth Hormone Replacement

Action: growth hormone replacement therapy Ontology label: Hormone Replacement Therapy NCIT:C15599

Agent: somatropin NCIT:C837

Standard therapy for types IB, II, and III, where the receptor is intact and there is no analogue of type IA's antibody-mediated treatment failure (that mechanism depends specifically on the immune system never having encountered endogenous GH, which is not the case here). Type IB patients characteristically show a positive growth response and immunologic tolerance to exogenous GH, exactly because some endogenous hormone was always present.

Mechanism Target:

RESTORES Insufficient Circulating Growth Hormone — Supplies exogenous GH to a system where the receptor is intact and immune tolerance to the hormone is already established, unlike type IA.

Show evidence (1 reference)

PMID:9814493 SUPPORT Human Clinical

"Insulin-like growth factor I (IGF-I) and IGF-binding protein 3 were low (5.2 +/- 2.0 ng/mL and 0.42 +/- 0.13 microg/mL, respectively; mean +/- SD) but rose normally with GH treatment."

Documents a normal IGF-1 response to exogenous GH in the type IB (GHRHR-null) cohort, evidence of an intact receptor pathway.

Show evidence (2 references)

PMID:9814493 SUPPORT Human Clinical

"Insulin-like growth factor I (IGF-I) and IGF-binding protein 3 were low (5.2 +/- 2.0 ng/mL and 0.42 +/- 0.13 microg/mL, respectively; mean +/- SD) but rose normally with GH treatment."

Direct evidence of treatment response in type IB.

DOI:10.3390/endocrines5030025 SUPPORT Human Clinical

"Children with GHD receive replacement therapy with daily injections of recombinant human GH (rhGH). RhGH therapy is effective in increasing short-term height gain and adult height in patients with GHD."

Current (2024) confirmation that daily rhGH replacement is standard, effective therapy for GHD generally, which applies to this entry's receptor-intact subtypes.

Long-Acting Weekly Growth Hormone Replacement

Action: growth hormone replacement therapy Ontology label: Hormone Replacement Therapy NCIT:C15599

Agent: somatrogon NCIT:C152396 somapacitan NCIT:C152394 lonapegsomatropin NCIT:C174805

Once-weekly recombinant GH formulations (somatrogon, somapacitan, lonapegsomatropin) reduce injection frequency from daily to weekly by extending the molecule's half-life (Fc-fusion, albumin-binding, or a transient prodrug linker, respectively), without changing the mechanism this entry's target_mechanisms edge already models for daily rhGH - they still supply exogenous GH to a receptor-intact system. Comparative trials test non-inferiority of weekly dosing against daily Genotropin on growth outcomes and treatment burden, rather than a different indication.

Mechanism Target:

RESTORES Insufficient Circulating Growth Hormone — Same mechanism as daily rhGH replacement above - supplies exogenous GH - with a pharmacokinetic modification (extended half-life) rather than a different mechanism of action.

Show evidence (1 reference)

clinicaltrials:NCT03831880 SUPPORT Human Clinical

"This is an open label randomized 24 week crossover trial assessing the treatment burden of a weekly growth hormone injection regimen (somatrogon) compared to a daily growth hormone injection regimen (Genotropin)."

The trial design directly compares the weekly and daily formulations as interchangeable GH-replacement regimens in the same patient population.

Show evidence (2 references)

clinicaltrials:NCT03831880 SUPPORT Human Clinical

"Approximately 90 children with growth hormone deficiency who have been stable on treatment with daily Genotropin will be enrolled."

Confirms the comparator population is GH-deficient children already established on daily replacement, the population this treatment entry addresses.

clinicaltrials:NCT04513171 SUPPORT Human Clinical

"This is a multicenter, randomized, open-labeled, positive controlled phase 2\&3 combined study to evaluate the safety and efficacy of weekly Y-shape pegylated somatropin, compared to daily somatropin (Norditropin®), in prepubertal, treatment-naive children with growth hormone deficiency."

A second, independent weekly-versus-daily comparative trial (pegylated somatropin) in the same treatment-naive GHD population.

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Biochemical Markers

Insulin-like growth factor 1 (IGF-1) (Low; normalizes with GH replacement)

Context: The principal biochemical readout of GH receptor signalling and, with IGFBP-3, the first-line screening test recommended before a formal GH stimulation test. Low in the untreated state and rising normally with exogenous GH in the receptor-intact subtypes modeled here (types IB, II, III) - the opposite pattern to Growth_Hormone_Insensitivity_Syndrome, where IGF-1 stays low despite GH replacement because the receptor itself is defective.

Show evidence (1 reference)

PMID:9814493 SUPPORT Human Clinical

"Insulin-like growth factor I (IGF-I) and IGF-binding protein 3 were low (5.2 +/- 2.0 ng/mL and 0.42 +/- 0.13 microg/mL, respectively; mean +/- SD) but rose normally with GH treatment."

The IGF-1 value and its normal rise on treatment in the type IB (GHRHR-null) cohort - the same quote used to evidence the "Loss of Growth Hormone Receptor Signalling" node, since this is the direct biochemical readout of that node's claim.

IGF-binding protein 3 (IGFBP-3) (Low; normalizes with GH replacement)

Context: Measured alongside IGF-1 as a complementary GH-axis biomarker; less dependent on nutritional status than IGF-1 alone, which is why diagnostic guidelines recommend both together.

Show evidence (1 reference)

PMID:9814493 SUPPORT Human Clinical

"Insulin-like growth factor I (IGF-I) and IGF-binding protein 3 were low (5.2 +/- 2.0 ng/mL and 0.42 +/- 0.13 microg/mL, respectively; mean +/- SD) but rose normally with GH treatment."

The IGFBP-3 value from the same sentence as the IGF-1 measurement above.

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Diagnosis

Growth hormone provocative (stimulation) stimulation testing

The diagnostic core of this entry: types IB, II, and III are defined by a subnormal peak GH response to pharmacologic stimulation (GHRH, L-dopa, clonidine, arginine, insulin, glucagon, or macimorelin), unlike type IA, which is instead defined molecularly by complete absence of the GH1 gene product (see the type IA sibling entry). Practice varies substantially across countries: preferred stimulation tests and their GH cutoffs differ, priming with sex steroids before testing in peripubertal children is now recommended in a majority of surveyed countries (with differing protocols), and the clinical pretest criteria that qualify a child for testing are inconsistently defined. Height, IGF-1, and bone age are used as additional diagnostic parameters in some countries' guidelines, on top of the stimulation test itself.

growth hormone stimulation test

Show evidence (3 references)

PMID:31707392 SUPPORT Human Clinical

"Preferred GH stimulation tests and chosen cutoffs vary substantially. Overall, a trend to lowering the GH cutoff was identified. Priming is becoming more popular and now recommended in 5 out of 9 countries; however, with different protocols."

Documents the international heterogeneity in stimulation-test choice, cutoff, and priming protocol - the basis for this node's caution against citing a single universal numeric cutoff.

PMID:31707392 SUPPORT Human Clinical

"Height, IGF-1, and bone age are additional parameters recommended in some countries."

Names the three additional parameters that supplement (but, per the same source, do not uniformly replace) the stimulation test itself.

PMID:9814493 SUPPORT Human Clinical

"Serum GH did not respond to provocative stimuli (GHRH, L-dopa, or clonidine)."

A worked example of the stimulation-test result (non-response to three separate agents) in a molecularly confirmed type IB patient.

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Prevalence

All Mendelian IGHD types combined

Birth Prevalence 1–9 per 100,000

Estimated frequency range of 1:4,000 to 1:10,000, cited generically for "GH deficiency" rather than broken down by molecular subtype. Curated here on the root entry rather than on the type IA sibling file, which explicitly deferred this parent-category rate to avoid overstating its own (rarer) frequency.

Show evidence (2 references)

PMID:12207163 SUPPORT Human Clinical

"Estimates of the frequency of GH deficiency range from 1:4,000 to 1:10,000."

Source for the birth-prevalence estimate. Note this figure is for GH deficiency broadly (isolated and otherwise), not this entry's four subtypes specifically - recorded as a range and flagged in notes rather than converted into a single rate_per_100000 to avoid false precision.

DOI:10.3390/endocrines5030025 SUPPORT Human Clinical

"Growth hormone deficiency (GHD) is the most frequent pituitary hormone deficiency in childhood, with an incidence of 1 in 4000–10,000 live births."

A 2024 review independently confirms the same incidence range with a current citation.

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Clinical Trials

NCT04786873 PHASE_III COMPLETED

Diagnostic trial of a single oral dose of macimorelin acetate as a GH stimulation test in pediatric patients with suspected GHD - relevant to this entry's diagnosis: section above, not to treatment.

Target Phenotypes: Reduced circulating growth hormone concentration HP:0034323

Show evidence (1 reference)

clinicaltrials:NCT04786873 SUPPORT

"The macimorelin test will be compared to a clonidine and an arginine test. Both are known standard stimulation tests."

An oral-secretagogue alternative to the injectable stimulation agents (GHRH, L-dopa, clonidine) named in the diagnosis: section, benchmarked against two of those standard agents.

NCT03831880 PHASE_III COMPLETED

Crossover trial of weekly somatrogon versus daily Genotropin, measuring patient/caregiver-reported treatment burden rather than growth outcome.

Target Phenotypes: Short stature HP:0004322

Show evidence (1 reference)

clinicaltrials:NCT03831880 SUPPORT

States the trial's comparative, treatment-burden-focused design.

NCT04513171 PHASE_III COMPLETED

Combined phase 2/3 trial of weekly Y-shape pegylated somatropin versus daily somatropin (Norditropin) in treatment-naive prepubertal children with GHD.

Target Phenotypes: Short stature HP:0004322

Show evidence (1 reference)

clinicaltrials:NCT04513171 SUPPORT

States the trial's comparative design and treatment-naive population.

NCT04614337 PHASE_II COMPLETED

Randomized trial of oral LUM-201 (a GH secretagogue receptor agonist, a small-molecule alternative to injectable rhGH) in naive-to-treatment prepubertal children with idiopathic GHD.

Target Phenotypes: Short stature HP:0004322

Show evidence (1 reference)

clinicaltrials:NCT04614337 SUPPORT

"This is a multi-national trial. The goals of the trial are to study LUM-201 as a possible treatment for Pediatric Growth Hormone Deficiency (PGHD) and investigate a predictive enrichment marker (PEM) strategy to select subjects likely to respond to therapy with LUM-201."

An oral small-molecule mechanism, distinct from the injectable protein-replacement treatments modeled above; not itself curated as a treatment entry in this PR since its mechanism (GH secretagogue receptor agonism) has not been independently verified against a quotable primary source beyond the trial registration.

NCT04806854 PHASE_II ACTIVE_NOT_RECRUITING

Single-center companion trial of oral LUM-201 in naive-to-treatment prepubertal children with idiopathic pediatric GHD.

Target Phenotypes: Short stature HP:0004322

Show evidence (1 reference)

clinicaltrials:NCT04806854 SUPPORT

"The goals of this single site trial are to study the pharmacokinetics (PK) and pharmacodynamics of LUM-201 and effects of LUM-201 administration on growth hormone release over time in children with idiopathic pediatric growth hormone deficiency (PGHD)."

The single-center companion study to NCT04614337, same investigational agent and population.

{ }

Source YAML

click to show

name: Isolated Growth Hormone Deficiency
creation_date: "2026-08-26T00:00:00Z"
category: Endocrine
disease_term:
  preferred_term: isolated congenital growth hormone deficiency
  term:
    id: MONDO:0000050
    label: isolated congenital growth hormone deficiency
description: >-
  Deficient pituitary growth hormone (GH) secretion in the absence of other
  anterior pituitary hormone deficiencies, producing proportionate short
  stature with normal body proportions and delayed bone age. Root umbrella
  entry over four Mendelian molecular-cause subtypes distinguished by mode of
  inheritance and by whether GH is completely absent or merely diminished:
  type IA (autosomal recessive, complete absence of endogenous GH from a
  severe GH1 loss-of-function lesion - curated at entity level as its own
  dismech entry and cross-referenced here), type IB (autosomal recessive,
  low but detectable GH, most often from a GHRHR loss-of-function variant
  and less often an intrinsic GH1 defect), type II (autosomal dominant, a
  GH1 intron-3 splice-site or splicing-enhancer variant that produces a
  dominant-negative 17.5-kDa GH isoform), and type III (X-linked, associated
  with the BTK region at Xq21.3-q22 or, in a separate route, with SOX3
  dosage at Xq26-27).

  Distinct from Growth_Hormone_Insensitivity_Syndrome (Laron syndrome and its
  molecular relatives), where GH secretion is normal or elevated but the
  receptor or a post-receptor signal is defective. Here the receptor is
  intact and it is the ligand itself - or, for type IB/III, the somatotroph's
  ability to make and release it - that is deficient. This is also why
  recombinant GH replacement is generally effective in types IB, II, and III,
  unlike in type IA, where treatment failure from anti-GH antibody formation
  is part of the disease itself (see the type IA entry).
parents:
- Growth Hormone Deficiency

has_subtypes:

- name: Type IA
  display_name: Type IA (GH1 severe loss-of-function; complete GH absence)
  description: >-
    The most severe Mendelian form: autosomal recessive, complete absence of
    endogenous GH from a severe GH1 loss-of-function lesion (most often a
    6.7-45 kb deletion, also frameshift and nonsense variants), with a
    distinctive treatment-failure mechanism (anti-GH antibody formation on
    replacement, because the immune system was never exposed to the
    hormone). Curated at entity level in
    kb/disorders/Isolated_Growth_Hormone_Deficiency_Type_IA.yaml
    (MONDO:0009876); it is cross-referenced here and not duplicated.
  subtype_term:
    preferred_term: isolated growth hormone deficiency type IA
    term:
      id: MONDO:0009876
      label: isolated growth hormone deficiency type IA
  genes:
  - preferred_term: GH1
    term:
      id: hgnc:4261
      label: GH1
  inheritance:
  - name: Autosomal recessive
    inheritance_term:
      preferred_term: Autosomal recessive inheritance
      term:
        id: HP:0000007
        label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:12207163
    reference_title: "Molecular and cellular basis of isolated dominant-negative growth hormone deficiency, IGHD type II: insights on the secretory pathway of peptide hormones."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Two forms are autosomal recessively (IGHD type IA and IB), one is
      autosomal dominantly (IGHD type II) and one X-linked inherited.
    explanation: >-
      Places type IA within the four-way classification this root entry
      models, alongside the other three subtypes below.

- name: Type IB
  display_name: Type IB (GHRHR or GH1 partial loss-of-function; diminished but detectable GH)
  description: >-
    Autosomal recessive, with low but detectable GH (unlike type IA's
    complete absence), significantly retarded bone age, and - because some
    endogenous GH was always present - a positive growth response and
    immunologic tolerance to exogenous GH therapy. The best-characterized
    molecular cause is an inactivating mutation of the GH-releasing hormone
    receptor (GHRHR), which leaves somatotrophs present but unable to
    receive the hypothalamic signal that drives GH synthesis and secretion;
    the founding description is "Dwarfism of Sindh," a consanguineous
    Pakistani kindred with a GHRHR nonsense mutation. An intrinsic GH1 defect
    is a much rarer alternative cause: a systematic sequencing survey found
    GH1 alterations in only 1.7% of subjects with the type IB phenotype,
    versus two-thirds of type IA families, and concluded that most type IB
    cases are not explained by GH1 itself.
  subtype_term:
    preferred_term: isolated growth hormone deficiency type IB
    term:
      id: MONDO:0013006
      label: isolated growth hormone deficiency type IB
  genes:
  - preferred_term: GHRHR
    term:
      id: hgnc:4266
      label: GHRHR
  - preferred_term: GH1
    term:
      id: hgnc:4261
      label: GH1
  inheritance:
  - name: Autosomal recessive
    inheritance_term:
      preferred_term: Autosomal recessive inheritance
      term:
        id: HP:0000007
        label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:9814493
    reference_title: "Phenotype and genetic analysis of a syndrome caused by an inactivating mutation in the growth hormone-releasing hormone receptor: Dwarfism of Sindh."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      DNA sequencing revealed a nonsense mutation (Glu50-->Stop) in the
      extracellular domain of the GHRH-R.
    explanation: >-
      The founding molecular description of GHRHR-caused type IB, in a
      consanguineous Pakistani kindred (dwarfism of Sindh).
  - reference: PMID:9432120
    reference_title: "Prevalence of human GH-1 gene alterations in patients with isolated growth hormone deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      the low frequency rate of 1.7% (2/119) of GH-1 gene mutations
      responsible for the most common phenotype of IGHD, namely type IB
    explanation: >-
      Quantifies how rarely GH1 itself, rather than GHRHR or another
      candidate gene, explains the type IB phenotype.

- name: Type II
  display_name: Type II (autosomal dominant GH1 intron-3 splice variant; dominant-negative 17.5-kDa isoform)
  description: >-
    Autosomal dominant, and the mechanistically richest subtype: a heterozygous
    variant at the GH1 intron-3 splice donor site (the recurrent "hot spot"
    IVS3+1G>A is the most frequently reported single lesion) or at a nearby
    exonic splicing enhancer causes skipping of exon 3, producing a
    truncated, dominant-negative 17.5-kDa GH isoform alongside normal 22-kDa
    GH from the other allele. The 17.5-kDa isoform disrupts GH secretory
    granules in a dose-dependent manner and separately triggers endoplasmic
    reticulum stress and caspase-mediated apoptosis in somatotrophs,
    destroying most of them in transgenic mouse models and causing anterior
    pituitary hypoplasia. Clinical severity is variable even among carriers
    of the same mutation, which splicing-enhancer-strength studies suggest
    may reflect how much 17.5-kDa isoform a given variant actually produces.
  subtype_term:
    preferred_term: isolated growth hormone deficiency type II
    term:
      id: MONDO:0008250
      label: isolated growth hormone deficiency type II
  genes:
  - preferred_term: GH1
    term:
      id: hgnc:4261
      label: GH1
  inheritance:
  - name: Autosomal dominant
    inheritance_term:
      preferred_term: Autosomal dominant inheritance
      term:
        id: HP:0000006
        label: Autosomal dominant inheritance
  evidence:
  - reference: PMID:17073157
    reference_title: "GH-1 gene splicing mutations: molecular basis of hereditary isolated growth hormone deficiency in children."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The "hot spot" of mutations is 5'-donor splicing site of GH-1 intron 3,
      while IVS3 +IG>A mutation can be regarded as the most incident in type
      II isolated growth hormone deficiency in the Russian population.
    explanation: >-
      Identifies the recurrent intron-3 donor-site hot spot underlying most
      type II cases in this cohort.
  - reference: PMID:12720086
    reference_title: "Disruption of exon definition produces a dominant-negative growth hormone isoform that causes somatotroph death and IGHD II."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Isolated growth hormone deficiency type II (IGHD II) is characterized
      by short stature due to dominant-negative mutations of the human
      growth hormone gene (GH1).
    explanation: >-
      Establishes the dominant-negative GH1 mechanism that defines this
      subtype, elaborated in the pathophysiology section below.

- name: Type III
  display_name: Type III (X-linked; BTK-region or SOX3)
  description: >-
    X-linked. The classic description (Fleisher syndrome) is a contiguous
    phenotype of X-linked hypogammaglobulinemia and isolated GH deficiency
    (XLA/GHD) mapping near the BTK gene at Xq21.3-q22, the same locus
    disrupted in Bruton's X-linked agammaglobulinemia
    (kb/disorders/X-linked_Agammaglobulinemia.yaml). The molecular basis of
    the GHD component is genuinely unresolved: in the kindred where it was
    originally described, BTK mRNA and protein were present at normal levels
    and the BTK coding sequence was normal, showing that XLA/GHD is not
    simply Bruton's XLA with an incidental growth phenotype, and a
    contiguous-deletion mechanism was explicitly excluded in three further
    XLA/GHD patients. A separate X-linked route is dosage alteration
    (duplication or deletion) of SOX3 at Xq26-27, which more typically
    produces infundibular hypoplasia with combined pituitary hormone
    deficiency rather than a strictly isolated GH deficit, though isolated
    GH deficiency has been reported as part of its phenotypic spectrum.
  subtype_term:
    preferred_term: isolated growth hormone deficiency type III
    term:
      id: MONDO:0010615
      label: isolated growth hormone deficiency type III
  genes:
  - preferred_term: BTK
    term:
      id: hgnc:1133
      label: BTK
  - preferred_term: SOX3
    term:
      id: hgnc:11199
      label: SOX3
  inheritance:
  - name: X-linked recessive
    inheritance_term:
      preferred_term: X-linked recessive inheritance
      term:
        id: HP:0001419
        label: X-linked recessive inheritance
    description: >-
      Applies to the BTK-region (Fleisher syndrome) route, in which affected
      males have both agammaglobulinemia and GH deficiency. The SOX3-dosage
      route is X-linked but its dominance/recessiveness is less clearly
      established, since reported carrier females have ranged from
      unaffected to mildly affected.
  evidence:
  - reference: PMID:7650402
    reference_title: "Molecular genetic analysis of X-linked hypogammaglobulinemia and isolated growth hormone deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In 1980 the clinical syndrome of X-linked hypogammaglobulinemia and
      isolated growth hormone deficiency (XLA/GHD) was described.
    explanation: >-
      Establishes the contiguous XLA/GHD phenotype this subtype is named
      for, distinct from Bruton's XLA alone.
  - reference: PMID:15800844
    reference_title: "Over- and underdosage of SOX3 is associated with infundibular hypoplasia and hypopituitarism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We conclude that both over- and underdosage of SOX3 are associated
      with similar phenotypes, consisting of infundibular hypoplasia and
      hypopituitarism but not necessarily MR.
    explanation: >-
      Establishes SOX3 dosage as a second, molecularly distinct X-linked
      route into this subtype's phenotype.

pathophysiology:

# --- Type IB arm ---
- name: GHRHR or GH1 Partial Loss-of-Function Variant
  role: trigger
  subtypes:
  - Type IB
  biological_scale: MOLECULAR
  description: >-
    Most commonly a biallelic inactivating GHRHR variant (the founding
    description is a nonsense mutation, Glu50Stop, in the receptor's
    extracellular domain, in a consanguineous Pakistani kindred); much less
    commonly an intrinsic GH1 variant, which a systematic sequencing survey
    found in only 1.7% of type IB subjects. Both converge on the same
    clinical picture - low but detectable GH, unlike type IA's complete
    absence.
  genetic_context:
    gene:
      preferred_term: GHRHR
      term:
        id: hgnc:4266
        label: GHRHR
    functional_impact_category: LOSS_OF_FUNCTION
    variant_origin: GERMLINE
    zygosity: HOMOZYGOUS
    description: >-
      Modeled on the GHRHR route, the better-characterized of the two
      genetic causes; a rarer intrinsic GH1 defect can produce the same
      downstream state by a distinct mechanism not captured by this
      genetic_context block.
  molecular_functions:
  - preferred_term: growth hormone-releasing hormone receptor activity
    term:
      id: GO:0016520
      label: growth hormone-releasing hormone receptor activity
    modifier: LOSS_OF_FUNCTION
  evidence:
  - reference: PMID:9814493
    reference_title: "Phenotype and genetic analysis of a syndrome caused by an inactivating mutation in the growth hormone-releasing hormone receptor: Dwarfism of Sindh."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      DNA sequencing revealed a nonsense mutation (Glu50-->Stop) in the
      extracellular domain of the GHRH-R.
    explanation: >-
      The variant defining the GHRHR route into this node.
  - reference: PMID:9432120
    reference_title: "Prevalence of human GH-1 gene alterations in patients with isolated growth hormone deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      the low frequency rate of 1.7% (2/119) of GH-1 gene mutations
      responsible for the most common phenotype of IGHD, namely type IB
    explanation: >-
      Quantifies the much rarer GH1 route bundled into this same trigger
      node.
  downstream:
  - target: Reduced Somatotroph Growth Hormone Synthesis and Secretion
    causal_link_type: DIRECT
    description: >-
      Loss of GHRH receptor signalling removes the hypothalamic drive for GH
      synthesis and secretion by intact somatotrophs; a GH1 defect acts more
      directly on the hormone itself. Either way the result is reduced, not
      absent, GH.

- name: Reduced Somatotroph Growth Hormone Synthesis and Secretion
  role: consequence
  subtypes:
  - Type IB
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: Somatotroph
    term:
      id: CL:0002312
      label: somatotroph
  biological_processes:
  - preferred_term: growth hormone secretion
    term:
      id: GO:0030252
      label: growth hormone secretion
    modifier: DECREASED
  description: >-
    Somatotrophs are present and capable of secretion, unlike the somatotroph
    loss modeled for type II below; without the GHRH signal (or with an
    intrinsic GH1 defect) they simply make and release less hormone.
  evidence:
  - reference: PMID:9814493
    reference_title: "Phenotype and genetic analysis of a syndrome caused by an inactivating mutation in the growth hormone-releasing hormone receptor: Dwarfism of Sindh."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Serum GH did not respond to provocative stimuli (GHRH, L-dopa, or
      clonidine).
    explanation: >-
      Documents the functional consequence of GHRHR loss on somatotroph GH
      output in the founding kindred.
  downstream:
  - target: Insufficient Circulating Growth Hormone
    causal_link_type: DIRECT

# --- Type II arm ---
- name: GH1 Intron-3 Splice-Site or Splicing-Enhancer Variant
  role: trigger
  subtypes:
  - Type II
  biological_scale: MOLECULAR
  genetic_context:
    gene:
      preferred_term: GH1
      term:
        id: hgnc:4261
        label: GH1
    functional_impact_category: DOMINANT_NEGATIVE
    variant_origin: GERMLINE
    zygosity: HETEROZYGOUS
    description: >-
      Most frequently the recurrent intron-3 donor splice-site variant
      IVS3+1G>A; other reported lesions weaken exon-3 splicing enhancers
      (dual enhancers are normally required for exon-3 definition) rather
      than disrupting the canonical splice site itself.
  description: >-
    A single mutant GH1 allele produces a mixture of normal transcript and
    an aberrantly spliced transcript lacking exon 3, while the other allele
    continues to produce normal transcript - the genetic basis of the
    dominant-negative phenotype elaborated in the nodes below.
  evidence:
  - reference: PMID:17073157
    reference_title: "GH-1 gene splicing mutations: molecular basis of hereditary isolated growth hormone deficiency in children."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The "hot spot" of mutations is 5'-donor splicing site of GH-1 intron 3,
      while IVS3 +IG>A mutation can be regarded as the most incident in type
      II isolated growth hormone deficiency in the Russian population.
    explanation: >-
      Identifies the recurrent hot-spot variant modeled on this node.
  - reference: PMID:12720086
    reference_title: "Disruption of exon definition produces a dominant-negative growth hormone isoform that causes somatotroph death and IGHD II."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      We demonstrate that dual splicing enhancers are required to ensure
      exon 3 definition to produce full-length 22-kDa hormone.
    explanation: >-
      Establishes the splicing-enhancer route into exon-3 skipping, distinct
      from a canonical splice-site variant but converging on the same
      downstream isoform. This is an in-vitro splicing-reporter finding, not
      a clinical observation.
  downstream:
  - target: Exon 3 Skipping and Dominant-Negative 17.5-kDa GH Isoform Production
    causal_link_type: DIRECT

- name: Exon 3 Skipping and Dominant-Negative 17.5-kDa GH Isoform Production
  role: central_effector
  subtypes:
  - Type II
  biological_scale: MOLECULAR
  description: >-
    The mutant allele's transcript skips exon 3, yielding a 17.5-kDa GH
    isoform lacking the residues exon 3 would have encoded (also described
    as del32-71 GH), co-expressed with normal 22-kDa GH from the wild-type
    allele. This isoform is not simply inactive - it actively interferes
    with the wild-type hormone's normal secretion, which is what makes the
    variant dominant-negative rather than a simple loss-of-function allele.
    Splicing-enhancer variants that only partially weaken exon-3 recognition
    produce variable amounts of the 17.5-kDa isoform, offering a candidate
    explanation for the clinical variability seen among type II patients.
  evidence:
  - reference: PMID:12720086
    reference_title: "Disruption of exon definition produces a dominant-negative growth hormone isoform that causes somatotroph death and IGHD II."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      mutations that cause exon 3 skipping and produce a dominant-negative
      17.5-kDa isoform in humans also cause a dose-dependent disruption of
      GH secretory vesicles when expressed in GC cells
    explanation: >-
      Names the 17.5-kDa isoform and its dose-dependent effect on secretory
      vesicles, the basis for the two downstream consequence nodes below.
      Quote trimmed to the GC-cell (IN_VITRO) clause; the same source
      sentence continues "...and transgenic mice," and that in-vivo
      corroboration is evidenced separately, as MODEL_ORGANISM, on the
      downstream "Anterior Pituitary Somatotroph Loss" node below.
  - reference: PMID:23736291
    reference_title: "Endoplasmic reticulum stress and apoptosis contribute to the pathogenesis of dominantly inherited isolated GH deficiency due to GH1 gene splice site mutations."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      An exon 3 deletion in GH (del32-71 GH) is produced from a mutant
      allele, whereas wild-type GH is produced from the other allele.
      Several studies have demonstrated a dominant negative effect of
      del32-71 GH on wild-type GH secretion
    explanation: >-
      Confirms the same isoform under an alternative name (del32-71 GH) and
      its dominant-negative effect on the co-expressed wild-type hormone.
  downstream:
  - target: Disruption of GH Secretory Granules
    causal_link_type: DIRECT
  - target: Endoplasmic Reticulum Stress and Somatotroph Apoptosis
    causal_link_type: DIRECT

- name: Disruption of GH Secretory Granules
  role: consequence
  subtypes:
  - Type II
  biological_scale: CELLULAR
  cellular_components:
  - preferred_term: secretory granule
    term:
      id: GO:0030141
      label: secretory granule
  biological_processes:
  - preferred_term: growth hormone secretion
    term:
      id: GO:0030252
      label: growth hormone secretion
    modifier: DECREASED
  description: >-
    Expression of the 17.5-kDa isoform causes a dose-dependent disruption of
    GH secretory vesicles, directly impairing regulated release of the
    co-packaged normal hormone independent of the apoptotic arm below.
  evidence:
  - reference: PMID:12720086
    reference_title: "Disruption of exon definition produces a dominant-negative growth hormone isoform that causes somatotroph death and IGHD II."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      mutations that cause exon 3 skipping and produce a dominant-negative
      17.5-kDa isoform in humans also cause a dose-dependent disruption of
      GH secretory vesicles when expressed in GC cells
    explanation: >-
      Direct evidence for the secretory-granule-disruption arm, observed in
      the GC cell line. The same source sentence also reports this in
      transgenic mice; that arm is evidenced separately, as MODEL_ORGANISM,
      on the "Anterior Pituitary Somatotroph Loss" node below rather than
      forced onto this quote.
  downstream:
  - target: Insufficient Circulating Growth Hormone
    causal_link_type: DIRECT

- name: Endoplasmic Reticulum Stress and Somatotroph Apoptosis
  role: consequence
  subtypes:
  - Type II
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: Somatotroph
    term:
      id: CL:0002312
      label: somatotroph
  biological_processes:
  - preferred_term: intrinsic apoptotic signaling pathway in response to endoplasmic reticulum stress
    term:
      id: GO:0070059
      label: intrinsic apoptotic signaling pathway in response to endoplasmic reticulum stress
    modifier: INCREASED
  description: >-
    Unfolded 17.5-kDa isoform accumulates in the endoplasmic reticulum and
    activates all three canonical ER stress-response arms (PERK, ATF6, and
    IRE1), with downstream caspase-3/7 activation and, in a subset of cell
    models, DNA fragmentation - a second, apoptotic route to reduced GH
    output that is independent of the granule-disruption arm above.
    Overexpressing the IRE1-downstream transcription factor XBP1(S) reversed
    the caspase activation in this system, identifying IRE1 signalling as
    load-bearing for the apoptotic effect rather than merely correlated
    with it.
  evidence:
  - reference: PMID:23736291
    reference_title: "Endoplasmic reticulum stress and apoptosis contribute to the pathogenesis of dominantly inherited isolated GH deficiency due to GH1 gene splice site mutations."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      del32-71 GH induction decreased cell viability, increased expression
      of 3 major ER stress response pathways
    explanation: >-
      Direct evidence for the ER-stress/apoptosis arm in a
      doxycycline-controlled cell model of the dominant-negative isoform.
      The three pathways named in the description (PERK, ATF6, IRE1) are the
      same sentence's parenthetical continuation in the source abstract.
  - reference: PMID:23736291
    reference_title: "Endoplasmic reticulum stress and apoptosis contribute to the pathogenesis of dominantly inherited isolated GH deficiency due to GH1 gene splice site mutations."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      overexpression of XBP1(S), a nuclear transcription factor downstream
      of IRE1, completely reversed the observed caspase activation
    explanation: >-
      Shows IRE1/XBP1(S) signalling is mechanistically load-bearing for the
      apoptotic effect, not just co-occurring with it.
  downstream:
  - target: Anterior Pituitary Somatotroph Loss
    causal_link_type: DIRECT

- name: Anterior Pituitary Somatotroph Loss
  role: consequence
  subtypes:
  - Type II
  biological_scale: TISSUE
  description: >-
    In transgenic mice, overexpression of the dominant-negative 17.5-kDa
    isoform destroyed the majority of somatotrophs and produced anterior
    pituitary hypoplasia. This structural consequence has been demonstrated
    in the mouse model rather than directly imaged in human type II
    patients; see the discussion below.
  evidence:
  - reference: PMID:12720086
    reference_title: "Disruption of exon definition produces a dominant-negative growth hormone isoform that causes somatotroph death and IGHD II."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      overexpression of the dominant-negative 17.5-kDa isoform also destroys
      the majority of somatotrophs, leading to anterior pituitary hypoplasia
      in transgenic mice.
    explanation: >-
      The transgenic mouse evidence for somatotroph destruction and
      resulting pituitary hypoplasia.
  downstream:
  - target: Insufficient Circulating Growth Hormone
    causal_link_type: DIRECT

# --- Type III arm ---
- name: BTK-Region Xq21.3-q22 Genetic Lesion
  role: trigger
  subtypes:
  - Type III
  biological_scale: MOLECULAR
  genetic_context:
    gene:
      preferred_term: BTK
      term:
        id: hgnc:1133
        label: BTK
    variant_origin: GERMLINE
    description: >-
      X-linked segregation of GH deficiency together with agammaglobulinemia
      is well established clinically in this region, but the specific
      genetic lesion responsible for the GHD component has not been
      identified: in the originally described kindred BTK mRNA and protein
      were both present at normal levels and the BTK coding sequence was
      normal, and a contiguous deletion spanning the region was explicitly
      excluded in three further XLA/GHD patients. This is a genuine
      knowledge gap (see discussions below), not a settled BTK mechanism.
  description: >-
    Named for the BTK locus because that is the established cause of the
    co-occurring agammaglobulinemia (Bruton's X-linked agammaglobulinemia,
    kb/disorders/X-linked_Agammaglobulinemia.yaml), not because BTK itself
    has been shown to cause the GH deficiency.
  evidence:
  - reference: PMID:7650402
    reference_title: "Molecular genetic analysis of X-linked hypogammaglobulinemia and isolated growth hormone deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      BTK mRNA was normal in size and abundance, and the mRNA sequence was
      normal over the coding region, except for a single silent mutation.
      BTK protein was present in normal amounts in PBMC of this patient.
      Thus, at the molecular level, XLA/GHD is a different disease entity
      from Bruton's XLA.
    explanation: >-
      PARTIAL: it establishes the X-linked locus and the clinical entity but
      actively refutes BTK itself as the GHD-causing gene in this patient,
      which is exactly the mechanistic gap this node records.
  - reference: PMID:7959728
    reference_title: "Isolation of cosmid and cDNA clones in the region surrounding the BTK gene at Xq21.3-q22."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Southern blot analysis using cDNA clones isolated from this region
      permitted us to exclude a contiguous deletion syndrome as an
      underlying defect in three patients with XLA and associated growth
      hormone deficiency.
    explanation: >-
      PARTIAL: rules out the most obvious structural explanation
      (contiguous deletion) without identifying an alternative.
  downstream:
  - target: Insufficient Circulating Growth Hormone
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      The intermediate cellular mechanism connecting this X-linked locus to
      reduced somatotroph GH output is unknown; only the clinical
      segregation and the anatomic locus are established.

- name: SOX3 Dosage Alteration
  role: trigger
  subtypes:
  - Type III
  biological_scale: MOLECULAR
  genetic_context:
    gene:
      preferred_term: SOX3
      term:
        id: hgnc:11199
        label: SOX3
    description: >-
      Duplication or deletion of the dosage-sensitive transcription factor
      SOX3 at Xq26-27; either direction of dosage change has been reported
      with infundibular hypoplasia and hypopituitarism, more typically
      combined pituitary hormone deficiency rather than a strictly isolated
      GH deficit.
  description: >-
    A molecularly distinct second route into the X-linked subtype, acting
    through hypothalamic-pituitary developmental patterning rather than
    through a locus linked to agammaglobulinemia.
  evidence:
  - reference: PMID:15800844
    reference_title: "Over- and underdosage of SOX3 is associated with infundibular hypoplasia and hypopituitarism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We conclude that both over- and underdosage of SOX3 are associated
      with similar phenotypes, consisting of infundibular hypoplasia and
      hypopituitarism but not necessarily MR.
    explanation: >-
      The dosage-sensitivity finding this node is built on.
  downstream:
  - target: Insufficient Circulating Growth Hormone
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Acts via disrupted hypothalamic-pituitary axis development
      (infundibular hypoplasia); the isolated-GHD presentation is part of a
      broader spectrum that more often includes other pituitary hormone
      deficiencies.

# --- Shared convergent chain ---
- name: Insufficient Circulating Growth Hormone
  role: central_effector
  biological_scale: ORGANISM
  description: >-
    The convergent state shared by types IB, II, and III: circulating GH is
    reduced by disruption of its synthesis, secretion, or the somatotroph
    population producing it - in contrast to type IA, where the GH1 gene
    product is absent altogether (curated separately). The route into this
    state differs by subtype (see the arms above), but the downstream
    consequence for growth is the same.
  evidence:
  - reference: PMID:17965963
    reference_title: "Isolated growth hormone deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In a small number of children with IGHD, defects in the GH,
      GH-releasing hormone receptor (GHRH-R), and GH1 genes have been
      identified.
    explanation: >-
      Ties the distinct genetic triggers modeled above to the shared
      downstream state of GH insufficiency.
  downstream:
  - target: Loss of Growth Hormone Receptor Signalling
    causal_link_type: DIRECT

- name: Loss of Growth Hormone Receptor Signalling
  role: consequence
  biological_scale: CELLULAR
  description: >-
    With less ligand available, growth hormone receptor signalling in
    peripheral target tissues (chiefly liver, driving IGF-1 generation) is
    correspondingly reduced. The receptor itself is normal throughout this
    entry, which is what distinguishes it mechanistically from
    Growth_Hormone_Insensitivity_Syndrome.
  biological_processes:
  - preferred_term: growth hormone receptor signaling pathway
    term:
      id: GO:0060396
      label: growth hormone receptor signaling pathway
    modifier: DECREASED
  evidence:
  - reference: PMID:9814493
    reference_title: "Phenotype and genetic analysis of a syndrome caused by an inactivating mutation in the growth hormone-releasing hormone receptor: Dwarfism of Sindh."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Insulin-like growth factor I (IGF-I) and IGF-binding protein 3 were
      low (5.2 +/- 2.0 ng/mL and 0.42 +/- 0.13 microg/mL, respectively;
      mean +/- SD) but rose normally with GH treatment.
    explanation: >-
      IGF-1/IGFBP-3 are the direct downstream readout of GH receptor
      signalling in the liver. Low IGF-1 in the untreated (ligand-deficient)
      state, rising normally once ligand is supplied, is direct evidence
      that receptor signalling tracks GH availability rather than being
      intrinsically impaired - exactly the claim this node makes.
  downstream:
  - target: Impaired Longitudinal Growth
    causal_link_type: DIRECT

- name: Impaired Longitudinal Growth
  role: consequence
  biological_scale: ORGANISM
  description: >-
    Reduced GH-dependent IGF-1 generation slows linear growth, producing
    proportionate short stature with delayed skeletal maturation - milder
    and later-declaring than type IA's universal severe dwarfism by six
    months, consistent with GH being reduced rather than absent.
  downstream:
  - target: Short Stature
    causal_link_type: DIRECT
  - target: Delayed Skeletal Maturation
    causal_link_type: DIRECT

phenotypes:

- category: Growth
  name: Short Stature
  description: >-
    Proportionate short stature, the defining clinical presentation shared
    by types IB, II, and III (type IA's more severe, earlier-onset course is
    curated on its own entry).
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  evidence:
  - reference: PMID:9814493
    reference_title: "Phenotype and genetic analysis of a syndrome caused by an inactivating mutation in the growth hormone-releasing hormone receptor: Dwarfism of Sindh."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Mean height was 7.2 SD below the norm, with mean adult heights of 130
      cm for males and 113.5 cm for females.
    explanation: >-
      Quantifies the severity of short stature in a GHRHR-null (type IB)
      cohort.

- category: Skeletal
  name: Delayed Skeletal Maturation
  description: >-
    Bone age lags behind chronological age, a standard finding across
    GH-deficiency subtypes generally, including MONDO's own definitional
    text for type IB ("significantly retarded bone age").
  phenotype_term:
    preferred_term: Delayed skeletal maturation
    term:
      id: HP:0002750
      label: Delayed skeletal maturation
  evidence:
  - reference: PMID:36960394
    reference_title: "A GHRHR founder mutation causes isolated growth hormone deficiency type IV in a consanguineous Pakistani family."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Patients with IGHD type IV (IGHD4) have a short stature, reduced
      serum GH levels, and delayed bone age.
    explanation: >-
      A direct statement of delayed bone age in a closely related,
      GHRHR-caused IGHD entity (type IV, out of this entry's declared
      scope - see notes). No cached source among the type IB/II/III
      literature actually screened for this entry (PMID:9814493,
      PMID:9432120, PMID:10678654, PMID:8528260, PMID:8288694) supplies a
      quotable bone-age sentence, despite MONDO's own def: text for type IB
      asserting "significantly retarded bone age." This quote is the
      closest verifiable substitute rather than a direct type IB/II/III
      finding, and the gap is recorded rather than papered over.

- category: Endocrine
  name: Reduced Circulating Growth Hormone Concentration
  description: >-
    Detectable but subnormal GH, the laboratory finding that separates types
    IB, II, and III from type IA's complete absence.
  phenotype_term:
    preferred_term: Reduced circulating growth hormone concentration
    term:
      id: HP:0034323
      label: Reduced circulating growth hormone concentration
  evidence:
  - reference: PMID:9814493
    reference_title: "Phenotype and genetic analysis of a syndrome caused by an inactivating mutation in the growth hormone-releasing hormone receptor: Dwarfism of Sindh."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Serum GH did not respond to provocative stimuli (GHRH, L-dopa, or
      clonidine).
    explanation: >-
      Documents blunted GH secretion in the type IB (GHRHR-null) cohort.

- category: Neurological
  name: Anterior Pituitary Hypoplasia
  description: >-
    Small anterior pituitary gland on MRI, present in a large majority of
    patients with idiopathic isolated GHD, not only in the combined
    (multi-hormone) deficiency forms - the human imaging counterpart of the
    somatotroph-loss pathophysiology modeled for type II (which is
    transgenic-mouse evidence; see the discussion on that node).
  phenotype_term:
    preferred_term: Anterior pituitary hypoplasia
    term:
      id: HP:0010627
      label: Anterior pituitary hypoplasia
  evidence:
  - reference: PMID:9802480
    reference_title: "MR imaging in idiopathic growth hormone deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Pituitary abnormalities were common in both groups (80% with isolated
      GHD, 93% with MPHD).
    explanation: >-
      Directly quantifies the pituitary-imaging abnormality rate in
      isolated GHD specifically (not just the combined-deficiency
      comparator group), from a 35-patient MRI series.

- category: Metabolic
  name: Neonatal Hypoglycemia
  description: >-
    Hypoglycemia presenting in the neonatal period, one of the few features
    that brings isolated GHD to clinical attention before growth failure
    becomes apparent.
  phenotype_term:
    preferred_term: Neonatal hypoglycemia
    term:
      id: HP:0001998
      label: Neonatal hypoglycemia
  evidence:
  - reference: PMID:9802480
    reference_title: "MR imaging in idiopathic growth hormone deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Breech delivery, neonatal hypoglycemia, jaundice, micropenis, or
      single central incisor occurred equally with both isolated GHD and
      MPHD.
    explanation: >-
      States explicitly that neonatal hypoglycemia occurs in isolated GHD
      at a rate statistically indistinguishable from the combined-deficiency
      comparator group, i.e., it is not an artifact of pooling with MPHD
      cases.

- category: Gastrointestinal
  name: Prolonged Neonatal Jaundice
  description: >-
    Neonatal jaundice persisting beyond the physiologic window, reported at
    a similar rate in isolated GHD and in combined pituitary hormone
    deficiency.
  phenotype_term:
    preferred_term: Prolonged neonatal jaundice
    term:
      id: HP:0006579
      label: Prolonged neonatal jaundice
  evidence:
  - reference: PMID:9802480
    reference_title: "MR imaging in idiopathic growth hormone deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Breech delivery, neonatal hypoglycemia, jaundice, micropenis, or
      single central incisor occurred equally with both isolated GHD and
      MPHD.
    explanation: >-
      Same source and same "occurred equally" statement as the neonatal
      hypoglycemia phenotype above, applied to jaundice.

- category: Genitourinary
  name: Micropenis
  description: >-
    Underdevelopment of the penis in affected males, reflecting the minor
    gonadotropin-independent role of GH in fetal genital growth; reported at
    a similar rate in isolated GHD and combined pituitary hormone
    deficiency.
  phenotype_term:
    preferred_term: Micropenis
    term:
      id: HP:0000054
      label: Micropenis
  evidence:
  - reference: PMID:9802480
    reference_title: "MR imaging in idiopathic growth hormone deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Breech delivery, neonatal hypoglycemia, jaundice, micropenis, or
      single central incisor occurred equally with both isolated GHD and
      MPHD.
    explanation: >-
      Same source and same "occurred equally" statement, applied to
      micropenis; a separate, larger GH-registry study (PMID:15198294)
      found micropenis in 55/100 hypoglycemic males but in a cohort that
      was mostly combined pituitary hormone deficiency (148/169) rather
      than isolated GHD (12/169), so it is cited here only as corroboration,
      not as the primary support.

genetic:

- name: GH1
  relationship_type: CAUSATIVE
  gene_term:
    preferred_term: GH1
    term:
      id: hgnc:4261
      label: GH1
  association: >-
    The gene most often implicated across this entry's subtypes: severe
    loss-of-function lesions cause type IA (curated separately), rare
    intrinsic variants are an uncommon cause of type IB, and heterozygous
    intron-3 splice or splicing-enhancer variants producing a
    dominant-negative 17.5-kDa isoform cause type II.
  evidence:
  - reference: PMID:9432120
    reference_title: "Prevalence of human GH-1 gene alterations in patients with isolated growth hormone deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Familial isolated growth hormone deficiency (IGHD) is associated with
      at least four Mendelian disorders. These include two forms that have
      autosomal recessive inheritance (IGHD types IA and IB) as well as
      autosomal dominant (IGHD type II) and X-linked (IGHD III) forms.
    explanation: >-
      The four-way classification GH1 (and the other genes below) sit
      within.

- name: GHRHR
  relationship_type: CAUSATIVE
  gene_term:
    preferred_term: GHRHR
    term:
      id: hgnc:4266
      label: GHRHR
  association: >-
    Biallelic inactivating variants cause type IB; the founding description
    is a homozygous nonsense mutation (Glu50Stop) in a consanguineous
    Pakistani kindred ("Dwarfism of Sindh"), later shown to be shared by
    other affected families.
  evidence:
  - reference: PMID:9814493
    reference_title: "Phenotype and genetic analysis of a syndrome caused by an inactivating mutation in the growth hormone-releasing hormone receptor: Dwarfism of Sindh."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This mutation predicts a severely truncated GHRH-R; it is identical to
      that recently reported in four patients from two other families.
    explanation: >-
      Shows the founding variant recurs across independent families rather
      than being a single private mutation.

- name: BTK
  relationship_type: RISK_FACTOR
  gene_term:
    preferred_term: BTK
    term:
      id: hgnc:1133
      label: BTK
  association: >-
    The gene disrupted in the well-established co-occurring
    agammaglobulinemia at this X-linked locus. Curated as RISK_FACTOR rather
    than CAUSATIVE for the GH-deficiency component specifically, because BTK
    coding sequence and protein were normal in the originally described
    XLA/GHD kindred and a contiguous deletion was excluded in three further
    patients - the GHD-causing element at this locus has not been
    identified (see discussions below).
  evidence:
  - reference: PMID:7650402
    reference_title: "Molecular genetic analysis of X-linked hypogammaglobulinemia and isolated growth hormone deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Thus, at the molecular level, XLA/GHD is a different disease entity
      from Bruton's XLA.
    explanation: >-
      PARTIAL: supports the X-linked locus and clinical entity while
      refuting BTK itself as the causal gene for the GHD component.

- name: SOX3
  relationship_type: CAUSATIVE
  gene_term:
    preferred_term: SOX3
    term:
      id: hgnc:11199
      label: SOX3
  association: >-
    Dosage alteration (duplication or deletion) at Xq26-27 causes a second,
    molecularly distinct X-linked route into this subtype, more often
    presenting as combined pituitary hormone deficiency with infundibular
    hypoplasia than as isolated GH deficiency.
  evidence:
  - reference: PMID:15800844
    reference_title: "Over- and underdosage of SOX3 is associated with infundibular hypoplasia and hypopituitarism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We conclude that both over- and underdosage of SOX3 are associated
      with similar phenotypes, consisting of infundibular hypoplasia and
      hypopituitarism but not necessarily MR.
    explanation: >-
      The dosage-sensitivity finding underlying this gene's inclusion.

inheritance:

- name: Autosomal recessive (types IA, IB)
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    Applies to type IA (curated separately) and type IB, both requiring
    biallelic loss of function at GH1 or, for type IB, most often GHRHR.
  evidence:
  - reference: PMID:12207163
    reference_title: "Molecular and cellular basis of isolated dominant-negative growth hormone deficiency, IGHD type II: insights on the secretory pathway of peptide hormones."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Two forms are autosomal recessively (IGHD type IA and IB), one is
      autosomal dominantly (IGHD type II) and one X-linked inherited.
    explanation: >-
      States the inheritance pattern for all four subtypes in one sentence.

- name: Autosomal dominant (type II)
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  description: >-
    A single heterozygous GH1 splice-affecting variant is sufficient,
    because the resulting 17.5-kDa isoform acts as a dominant negative
    against the normal protein produced by the other allele.
  evidence:
  - reference: PMID:12720086
    reference_title: "Disruption of exon definition produces a dominant-negative growth hormone isoform that causes somatotroph death and IGHD II."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Isolated growth hormone deficiency type II (IGHD II) is characterized
      by short stature due to dominant-negative mutations of the human
      growth hormone gene (GH1).
    explanation: >-
      States the dominant-negative, autosomal dominant basis of type II.

- name: X-linked recessive (type III)
  inheritance_term:
    preferred_term: X-linked recessive inheritance
    term:
      id: HP:0001419
      label: X-linked recessive inheritance
  description: >-
    Applies to the BTK-region (Fleisher syndrome) route, in which affected
    hemizygous males have both agammaglobulinemia and GH deficiency.
  evidence:
  - reference: PMID:7650402
    reference_title: "Molecular genetic analysis of X-linked hypogammaglobulinemia and isolated growth hormone deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In 1980 the clinical syndrome of X-linked hypogammaglobulinemia and
      isolated growth hormone deficiency (XLA/GHD) was described.
    explanation: >-
      The clinical description this X-linked pattern is drawn from.

biochemical:

- name: Insulin-like growth factor 1 (IGF-1)
  context: >-
    The principal biochemical readout of GH receptor signalling and, with
    IGFBP-3, the first-line screening test recommended before a formal GH
    stimulation test. Low in the untreated state and rising normally with
    exogenous GH in the receptor-intact subtypes modeled here (types IB,
    II, III) - the opposite pattern to Growth_Hormone_Insensitivity_Syndrome,
    where IGF-1 stays low despite GH replacement because the receptor
    itself is defective.
  presence: Low; normalizes with GH replacement
  biomarker_term:
    preferred_term: insulin-like growth factor 1
  evidence:
  - reference: PMID:9814493
    reference_title: "Phenotype and genetic analysis of a syndrome caused by an inactivating mutation in the growth hormone-releasing hormone receptor: Dwarfism of Sindh."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Insulin-like growth factor I (IGF-I) and IGF-binding protein 3 were
      low (5.2 +/- 2.0 ng/mL and 0.42 +/- 0.13 microg/mL, respectively;
      mean +/- SD) but rose normally with GH treatment.
    explanation: >-
      The IGF-1 value and its normal rise on treatment in the type IB
      (GHRHR-null) cohort - the same quote used to evidence the "Loss of
      Growth Hormone Receptor Signalling" node, since this is the direct
      biochemical readout of that node's claim.

- name: IGF-binding protein 3 (IGFBP-3)
  context: >-
    Measured alongside IGF-1 as a complementary GH-axis biomarker; less
    dependent on nutritional status than IGF-1 alone, which is why
    diagnostic guidelines recommend both together.
  presence: Low; normalizes with GH replacement
  biomarker_term:
    preferred_term: insulin-like growth factor binding protein 3
  evidence:
  - reference: PMID:9814493
    reference_title: "Phenotype and genetic analysis of a syndrome caused by an inactivating mutation in the growth hormone-releasing hormone receptor: Dwarfism of Sindh."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Insulin-like growth factor I (IGF-I) and IGF-binding protein 3 were
      low (5.2 +/- 2.0 ng/mL and 0.42 +/- 0.13 microg/mL, respectively;
      mean +/- SD) but rose normally with GH treatment.
    explanation: >-
      The IGFBP-3 value from the same sentence as the IGF-1 measurement
      above.

diagnosis:

- name: Growth hormone provocative (stimulation) stimulation testing
  description: >-
    The diagnostic core of this entry: types IB, II, and III are defined by
    a subnormal peak GH response to pharmacologic stimulation (GHRH,
    L-dopa, clonidine, arginine, insulin, glucagon, or macimorelin), unlike
    type IA, which is instead defined molecularly by complete absence of
    the GH1 gene product (see the type IA sibling entry). Practice varies
    substantially across countries: preferred stimulation tests and their
    GH cutoffs differ, priming with sex steroids before testing in
    peripubertal children is now recommended in a majority of surveyed
    countries (with differing protocols), and the clinical pretest criteria
    that qualify a child for testing are inconsistently defined. Height,
    IGF-1, and bone age are used as additional diagnostic parameters in
    some countries' guidelines, on top of the stimulation test itself.
  diagnosis_term:
    preferred_term: growth hormone stimulation test
  evidence:
  - reference: PMID:31707392
    reference_title: "GHD Diagnostics in Europe and the US: An Audit of National Guidelines and Practice."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Preferred GH stimulation tests and chosen cutoffs vary substantially.
      Overall, a trend to lowering the GH cutoff was identified. Priming is
      becoming more popular and now recommended in 5 out of 9 countries;
      however, with different protocols.
    explanation: >-
      Documents the international heterogeneity in stimulation-test choice,
      cutoff, and priming protocol - the basis for this node's caution
      against citing a single universal numeric cutoff.
  - reference: PMID:31707392
    reference_title: "GHD Diagnostics in Europe and the US: An Audit of National Guidelines and Practice."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Height, IGF-1, and bone age are additional parameters recommended in
      some countries.
    explanation: >-
      Names the three additional parameters that supplement (but, per the
      same source, do not uniformly replace) the stimulation test itself.
  - reference: PMID:9814493
    reference_title: "Phenotype and genetic analysis of a syndrome caused by an inactivating mutation in the growth hormone-releasing hormone receptor: Dwarfism of Sindh."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Serum GH did not respond to provocative stimuli (GHRH, L-dopa, or
      clonidine).
    explanation: >-
      A worked example of the stimulation-test result (non-response to
      three separate agents) in a molecularly confirmed type IB patient.

treatments:

- name: Recombinant Human Growth Hormone Replacement
  description: >-
    Standard therapy for types IB, II, and III, where the receptor is intact
    and there is no analogue of type IA's antibody-mediated treatment
    failure (that mechanism depends specifically on the immune system never
    having encountered endogenous GH, which is not the case here). Type IB
    patients characteristically show a positive growth response and
    immunologic tolerance to exogenous GH, exactly because some endogenous
    hormone was always present.
  therapeutic_modality: PROTEIN_REPLACEMENT
  treatment_term:
    preferred_term: growth hormone replacement therapy
    term:
      id: NCIT:C15599
      label: Hormone Replacement Therapy
    therapeutic_agent:
    - preferred_term: somatropin
      term:
        id: NCIT:C837
        label: Somatropin
  target_mechanisms:
  - target: Insufficient Circulating Growth Hormone
    treatment_effect: RESTORES
    description: >-
      Supplies exogenous GH to a system where the receptor is intact and
      immune tolerance to the hormone is already established, unlike type
      IA.
    evidence:
    - reference: PMID:9814493
      reference_title: "Phenotype and genetic analysis of a syndrome caused by an inactivating mutation in the growth hormone-releasing hormone receptor: Dwarfism of Sindh."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Insulin-like growth factor I (IGF-I) and IGF-binding protein 3 were
        low (5.2 +/- 2.0 ng/mL and 0.42 +/- 0.13 microg/mL, respectively;
        mean +/- SD) but rose normally with GH treatment.
      explanation: >-
        Documents a normal IGF-1 response to exogenous GH in the type IB
        (GHRHR-null) cohort, evidence of an intact receptor pathway.
  evidence:
  - reference: PMID:9814493
    reference_title: "Phenotype and genetic analysis of a syndrome caused by an inactivating mutation in the growth hormone-releasing hormone receptor: Dwarfism of Sindh."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Insulin-like growth factor I (IGF-I) and IGF-binding protein 3 were
      low (5.2 +/- 2.0 ng/mL and 0.42 +/- 0.13 microg/mL, respectively;
      mean +/- SD) but rose normally with GH treatment.
    explanation: >-
      Direct evidence of treatment response in type IB.
  - reference: DOI:10.3390/endocrines5030025
    reference_title: "Isolated Growth Hormone Deficiency"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Children with GHD receive replacement therapy with daily injections of
      recombinant human GH (rhGH). RhGH therapy is effective in increasing
      short-term height gain and adult height in patients with GHD.
    explanation: >-
      Current (2024) confirmation that daily rhGH replacement is standard,
      effective therapy for GHD generally, which applies to this entry's
      receptor-intact subtypes.

- name: Long-Acting Weekly Growth Hormone Replacement
  description: >-
    Once-weekly recombinant GH formulations (somatrogon, somapacitan,
    lonapegsomatropin) reduce injection frequency from daily to weekly by
    extending the molecule's half-life (Fc-fusion, albumin-binding, or a
    transient prodrug linker, respectively), without changing the
    mechanism this entry's target_mechanisms edge already models for daily
    rhGH - they still supply exogenous GH to a receptor-intact system.
    Comparative trials test non-inferiority of weekly dosing against daily
    Genotropin on growth outcomes and treatment burden, rather than a
    different indication.
  therapeutic_modality: PROTEIN_REPLACEMENT
  treatment_term:
    preferred_term: growth hormone replacement therapy
    term:
      id: NCIT:C15599
      label: Hormone Replacement Therapy
    therapeutic_agent:
    - preferred_term: somatrogon
      term:
        id: NCIT:C152396
        label: Somatrogon
    - preferred_term: somapacitan
      term:
        id: NCIT:C152394
        label: Somapacitan
    - preferred_term: lonapegsomatropin
      term:
        id: NCIT:C174805
        label: Lonapegsomatropin
  target_mechanisms:
  - target: Insufficient Circulating Growth Hormone
    treatment_effect: RESTORES
    description: >-
      Same mechanism as daily rhGH replacement above - supplies exogenous
      GH - with a pharmacokinetic modification (extended half-life) rather
      than a different mechanism of action.
    evidence:
    - reference: clinicaltrials:NCT03831880
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        This is an open label randomized 24 week crossover trial assessing
        the treatment burden of a weekly growth hormone injection regimen
        (somatrogon) compared to a daily growth hormone injection regimen
        (Genotropin).
      explanation: >-
        The trial design directly compares the weekly and daily
        formulations as interchangeable GH-replacement regimens in the
        same patient population.
  evidence:
  - reference: clinicaltrials:NCT03831880
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Approximately 90 children with growth hormone deficiency who have
      been stable on treatment with daily Genotropin will be enrolled.
    explanation: >-
      Confirms the comparator population is GH-deficient children already
      established on daily replacement, the population this treatment
      entry addresses.
  - reference: clinicaltrials:NCT04513171
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This is a multicenter, randomized, open-labeled, positive controlled
      phase 2\&3 combined study to evaluate the safety and efficacy of
      weekly Y-shape pegylated somatropin, compared to daily somatropin
      (Norditropin®), in prepubertal, treatment-naive children with
      growth hormone deficiency.
    explanation: >-
      A second, independent weekly-versus-daily comparative trial
      (pegylated somatropin) in the same treatment-naive GHD population.

clinical_trials:

- name: NCT04786873
  phase: PHASE_III
  status: COMPLETED
  description: >-
    Diagnostic trial of a single oral dose of macimorelin acetate as a GH
    stimulation test in pediatric patients with suspected GHD - relevant to
    this entry's diagnosis: section above, not to treatment.
  target_phenotypes:
  - preferred_term: Reduced circulating growth hormone concentration
    term:
      id: HP:0034323
      label: Reduced circulating growth hormone concentration
  evidence:
  - reference: clinicaltrials:NCT04786873
    supports: SUPPORT
    snippet: >-
      The macimorelin test will be compared to a clonidine and an arginine
      test. Both are known standard stimulation tests.
    explanation: >-
      An oral-secretagogue alternative to the injectable stimulation
      agents (GHRH, L-dopa, clonidine) named in the diagnosis: section,
      benchmarked against two of those standard agents.

- name: NCT03831880
  phase: PHASE_III
  status: COMPLETED
  description: >-
    Crossover trial of weekly somatrogon versus daily Genotropin, measuring
    patient/caregiver-reported treatment burden rather than growth outcome.
  target_phenotypes:
  - preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  evidence:
  - reference: clinicaltrials:NCT03831880
    supports: SUPPORT
    snippet: >-
      This is an open label randomized 24 week crossover trial assessing
      the treatment burden of a weekly growth hormone injection regimen
      (somatrogon) compared to a daily growth hormone injection regimen
      (Genotropin).
    explanation: >-
      States the trial's comparative, treatment-burden-focused design.

- name: NCT04513171
  phase: PHASE_III
  status: COMPLETED
  description: >-
    Combined phase 2/3 trial of weekly Y-shape pegylated somatropin versus
    daily somatropin (Norditropin) in treatment-naive prepubertal children
    with GHD.
  target_phenotypes:
  - preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  evidence:
  - reference: clinicaltrials:NCT04513171
    supports: SUPPORT
    snippet: >-
      This is a multicenter, randomized, open-labeled, positive controlled
      phase 2\&3 combined study to evaluate the safety and efficacy of
      weekly Y-shape pegylated somatropin, compared to daily somatropin
      (Norditropin®), in prepubertal, treatment-naive children with
      growth hormone deficiency.
    explanation: >-
      States the trial's comparative design and treatment-naive population.

- name: NCT04614337
  phase: PHASE_II
  status: COMPLETED
  description: >-
    Randomized trial of oral LUM-201 (a GH secretagogue receptor agonist,
    a small-molecule alternative to injectable rhGH) in naive-to-treatment
    prepubertal children with idiopathic GHD.
  target_phenotypes:
  - preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  evidence:
  - reference: clinicaltrials:NCT04614337
    supports: SUPPORT
    snippet: >-
      This is a multi-national trial. The goals of the trial are to study
      LUM-201 as a possible treatment for Pediatric Growth Hormone
      Deficiency (PGHD) and investigate a predictive enrichment marker
      (PEM) strategy to select subjects likely to respond to therapy with
      LUM-201.
    explanation: >-
      An oral small-molecule mechanism, distinct from the injectable
      protein-replacement treatments modeled above; not itself curated as
      a treatment entry in this PR since its mechanism (GH secretagogue
      receptor agonism) has not been independently verified against a
      quotable primary source beyond the trial registration.

- name: NCT04806854
  phase: PHASE_II
  status: ACTIVE_NOT_RECRUITING
  description: >-
    Single-center companion trial of oral LUM-201 in naive-to-treatment
    prepubertal children with idiopathic pediatric GHD.
  target_phenotypes:
  - preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  evidence:
  - reference: clinicaltrials:NCT04806854
    supports: SUPPORT
    snippet: >-
      The goals of this single site trial are to study the
      pharmacokinetics (PK) and pharmacodynamics of LUM-201 and effects of
      LUM-201 administration on growth hormone release over time in
      children with idiopathic pediatric growth hormone deficiency (PGHD).
    explanation: >-
      The single-center companion study to NCT04614337, same investigational
      agent and population.

prevalence:

- population: All Mendelian IGHD types combined
  measure_type: BIRTH_PREVALENCE
  prevalence_class: BAND_1_9_PER_100000
  notes: >-
    Estimated frequency range of 1:4,000 to 1:10,000, cited generically for
    "GH deficiency" rather than broken down by molecular subtype. Curated
    here on the root entry rather than on the type IA sibling file, which
    explicitly deferred this parent-category rate to avoid overstating its
    own (rarer) frequency.
  evidence:
  - reference: PMID:12207163
    reference_title: "Molecular and cellular basis of isolated dominant-negative growth hormone deficiency, IGHD type II: insights on the secretory pathway of peptide hormones."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Estimates of the frequency of GH deficiency range from 1:4,000 to
      1:10,000.
    explanation: >-
      Source for the birth-prevalence estimate. Note this figure is for GH
      deficiency broadly (isolated and otherwise), not this entry's four
      subtypes specifically - recorded as a range and flagged in notes
      rather than converted into a single rate_per_100000 to avoid false
      precision.
  - reference: DOI:10.3390/endocrines5030025
    reference_title: "Isolated Growth Hormone Deficiency"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Growth hormone deficiency (GHD) is the most frequent pituitary hormone
      deficiency in childhood, with an incidence of 1 in 4000–10,000 live
      births.
    explanation: >-
      A 2024 review independently confirms the same incidence range with a
      current citation.

discussions:

- discussion_id: gap_type3_btk_mechanism_unknown
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    What is the actual genetic lesion responsible for the growth hormone
    deficiency component of X-linked hypogammaglobulinemia and isolated
    growth hormone deficiency (XLA/GHD, "Fleisher syndrome"), if it is not
    BTK itself?
  attaches_to:
  - pathophysiology#BTK-Region Xq21.3-q22 Genetic Lesion
  - genetic#BTK
  rationale: >-
    The clinical entity is well established and clearly X-linked, but the
    two molecular studies available on the founding kindred and a further
    three XLA/GHD patients both point away from BTK as the GHD-causing
    gene: BTK mRNA, protein, and coding sequence were normal in the original
    patient, and a contiguous deletion spanning the flanking region was
    explicitly excluded in three more patients. Type III is therefore
    curated with BTK as a RISK_FACTOR / locus marker rather than a
    CAUSATIVE gene for the GHD arm specifically, and the causal_link_type on
    this node's downstream edge is INDIRECT_UNKNOWN_INTERMEDIATES rather
    than DIRECT. No later molecular candidate for the actual GHD gene at
    this locus was found in the literature searched for this entry.
  evidence:
  - reference: PMID:7650402
    reference_title: "Molecular genetic analysis of X-linked hypogammaglobulinemia and isolated growth hormone deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These results suggest that undescribed genes critical for B cell
      development and growth hormone production exist on the X chromosome.
    explanation: >-
      The original authors' own framing of the open question, over two
      decades before this entry was curated.
  proposed_experiments:
  - experiment_id: xla_ghd_locus_fine_mapping
    name: Whole-genome sequencing and fine mapping of remaining XLA/GHD kindreds
    description: >-
      Apply modern long-read sequencing and RNA-seq to XLA/GHD families
      (rather than the Southern-blot and cDNA-clone methods available at the
      time of the founding studies) to identify structural variants,
      regulatory-region lesions, or a second gene at Xq21.3-q22 that
      segregates with the GHD component independent of BTK status.

- discussion_id: gap_type2_mouse_pituitary_hypoplasia_human_extrapolation
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  prompt: >-
    Does the anterior pituitary hypoplasia and majority somatotroph loss
    seen in transgenic mice overexpressing the dominant-negative 17.5-kDa GH
    isoform actually occur to the same degree in human type II patients, or
    is the human disease driven predominantly by the (also demonstrated)
    secretory-granule-disruption arm without comparable cell loss?
  attaches_to:
  - pathophysiology#Anterior Pituitary Somatotroph Loss
  rationale: >-
    The somatotroph-destruction and pituitary-hypoplasia finding comes from
    a transgenic mouse model overexpressing the isoform, not from pituitary
    histology or imaging in human type II patients, who are diagnosed and
    followed clinically and biochemically rather than by pituitary biopsy.
    Mouse overexpression systems can produce isoform levels and expression
    patterns that do not match the heterozygous dosage in human patients
    (one mutant allele plus one normal allele, rather than an overexpression
    transgene), so the degree of somatotroph loss - as opposed to reversible
    secretory dysfunction - in human disease is not established by this
    evidence alone.
  proposed_experiments:
  - experiment_id: type2_pituitary_mri_volumetry
    name: Pituitary MRI volumetry in molecularly confirmed type II patients
    description: >-
      Compare anterior pituitary volume by MRI between type II patients
      (stratified by the specific GH1 variant and its reported
      splicing-enhancer strength) and type IB/unaffected relatives, to test
      whether structural pituitary hypoplasia is present in humans and
      whether it
      scales with predicted 17.5-kDa isoform dose as the mouse and cell data
      suggest.

notes: >-
  Scope relative to MONDO. MONDO:0000050 has seven child terms in its OAK
  relationship closure: the four requested here (types IA, IB, II, III) plus
  MONDO:0032567/MONDO:0032569 (types 4 and 5) and MONDO:0009879 (short
  stature due to a GH qualitative anomaly - Kowarski syndrome, bioinactive
  GH with normal or elevated immunoassayable GH but reduced bioactivity, a
  mechanistically distinct entity from the four quantitative-deficiency
  subtypes modeled here). These three are deliberately out of scope for this
  entry and not modeled as subtypes; a future curator extending this entry
  to types 4/5 or to Kowarski syndrome does not need to rediscover this via
  OAK.

  Type IA is deliberately not duplicated. It is fully curated in
  kb/disorders/Isolated_Growth_Hormone_Deficiency_Type_IA.yaml, which
  already declares parents: [Isolated Growth Hormone Deficiency, Growth
  Hormone Deficiency] pointing back at this entry - so the parent-child link
  is bidirectional even though `has_subtypes` cannot itself point at an
  external file. The `Type IA` block above is a pointer only (`subtype_term`
  plus enough evidence to justify its place in the classification), matching
  the pattern already used for Appendiceal_Neoplasm.yaml /
  Appendiceal_Neuroendocrine_Tumor.yaml and
  Growth_Hormone_Insensitivity_Syndrome.yaml / IGF1_Deficiency.yaml.

  Contrast with Growth_Hormone_Insensitivity_Syndrome (Laron syndrome and
  its molecular relatives) is stated in the top-level description and
  repeated on the shared "Loss of Growth Hormone Receptor Signalling" node,
  since it is the single most important disambiguation for this entry: GHIS
  has normal-to-high GH and a broken receptor/post-receptor signal; this
  entry has an intact receptor and a deficient ligand (or, for type III, a
  deficient somatotroph population by an unknown mechanism).

  Type III genetics is curated honestly rather than simply repeating MONDO's
  RO:0004003 BTK relationship. MONDO:0010615 asserts `relationship: RO:0004003
  HGNC:1133 ! BTK`, but the two molecular papers available on this locus
  (Stewart et al. 1995, Vorechovsky et al. 1994) both argue against BTK
  itself as the GHD-causing gene - BTK sequence and protein were normal in
  the founding kindred, and a contiguous deletion was excluded in three
  further patients. Rather than silently following the MONDO relationship
  or silently contradicting it, this entry curates BTK as `RISK_FACTOR`
  (not `CAUSATIVE`) for the GHD component, uses `INDIRECT_UNKNOWN_INTERMEDIATES`
  on the corresponding causal edge, and records the gap as an open
  `KNOWLEDGE_GAP` discussion with its own PMIDs, per the instruction in
  CLAUDE.md's design-decisions guidance to surface a decision that looks
  wrong or stale rather than silently contradict it.

  GHRHR is modeled here under Type IB (MONDO:0013006), not a separate Type
  IV, and that choice is a documented departure from part of the current
  literature rather than an oversight. Three independent facts are in
  tension: (1) the source issue explicitly asked for "type IB (GH1/GHRHR
  splice and missense)"; (2) MONDO:0013006's own `def:` text names both
  "the GH1 or GHRHR genes" as the material basis of type IB, and its
  synonym list includes "dwarfism of Sindh" - the exact
  GHRHR-founder-mutation kindred this entry cites (PMID:9814493) - while
  its structured
  `relationship: RO:0004003` edge names only GH1 (HGNC:4261); (3) MONDO
  separately maintains MONDO:0032567 "isolated growth hormone deficiency,
  type 4" (OMIM:618157), whose own `relationship: RO:0004003` edge names
  GHRHR (HGNC:4266) specifically, and a 2023 primary source on a GHRHR
  founder mutation (PMID:36960394) explicitly assigns GHRHR-caused disease
  to "type IV" while stating type IB is caused by GH1 alone - directly
  contradicting MONDO:0013006's own def: text in the same breath its
  abstract also contradicts itself on the OMIM number for type IB (612781
  vs. 617281 within one paragraph). This is therefore a genuine,
  unresolved classification ambiguity in the field/OMIM/MONDO literature,
  not a single wrong fact this entry can silently correct. Given the
  issue's explicit instruction and MONDO:0013006's own def:/synonym
  support, this entry keeps GHRHR under Type IB and leaves MONDO:0032567
  (type 4/IV) out of scope alongside type 5 (see the scope note above) -
  but flags this for a future MONDO curation pass that might split IB into
  a GH1-only entity and reassign GHRHR cases to type IV. Verified via
  `uv run runoak -i sqlite:obo:mondo info MONDO:0013006 MONDO:0032567 -O obo`.

  GeneReviews baseline: checked, not found. PubMed searches for
  "isolated growth hormone deficiency[TI] GeneReviews[TI]" and several
  broader variants returned only false positives (Temple syndrome,
  sepiapterin reductase deficiency, GLI3-related Pallister-Hall syndrome,
  PIK3CA-related overgrowth spectrum, GNAS inactivation disorders, G6PC3
  deficiency, AIP familial isolated pituitary adenomas) - the same
  false-positive pattern already recorded on the type IA sibling entry, now
  confirmed independently for the root term as well. No GeneReviews chapter
  on isolated GH deficiency appears to exist.

  Orphanet structured citation not available for this session. `just
  refresh-orphadata` failed with a checksum mismatch against the pinned
  manifest (the live Orphadata en_product1.xml no longer matches the sha256
  recorded in data/orphadata/MANIFEST.yaml) - an upstream drift issue
  unrelated to this curation, not something this entry's author should paper
  over by re-pinning the manifest unreviewed. Prevalence is instead sourced
  from PMID:12207163's PubMed abstract, with the parent-category caveat
  spelled out in the prevalence `notes`.

  HP:0034323 (Reduced circulating growth hormone concentration) is the
  correct CURIE for this concept; the type IA sibling entry's `notes` prose
  cites it as "HP:0034331," which is a typo in that file's free text (not a
  bound `term:`, so it did not fail validation there). Recorded here so the
  correct ID is not mistakenly copied from the wrong source in a future
  edit; not fixed in the sibling file as part of this PR, since it is
  free-text prose in a file this task did not otherwise touch.

  Deep research. A falcon (Edison/FutureHouse) provider run completed
  (research/Isolated_Growth_Hormone_Deficiency-deep-research-falcon.md). Its
  own reference validation reports 11/12 identifiers resolved (one DOI,
  10.17458/per.vol16.2018.dd.geneticmutationsghigf, cited 9 times in the
  report as "domene2018geneticmutationsin," failed to resolve against
  Crossref and DataCite and is NOT used anywhere in this entry), and only
  5/11 resolved references scored on topic (0 off topic, so the remainder
  are undecided rather than cleared) - `needs_review: true`. Every PMID and
  DOI actually cited in this file was independently found via direct PubMed
  E-utilities / Crossref search and fetched with `just fetch-reference`, not
  taken on trust from the falcon narrative; the one exception is
  DOI:10.3390/endocrines5030025 (Ibba et al. 2024), which the falcon report
  also surfaced and which this entry independently verified and fetched
  before citing. The falcon report's own gene table corroborates this
  entry's modeling choice for type III ("IGHD III - SOX3 or BTK, X-linked
  ... biologically heterogeneous and may not remain strictly isolated") and
  additionally names RNPC3 (minor-spliceosome) and occasionally GHSR as
  further, more recently reported IGHD genes; both are outside the four
  subtypes the source issue asked for and are deliberately not modeled here,
  recorded so a future extension does not need to rediscover them.

references:
- reference: PMID:17965963
  title: "Isolated growth hormone deficiency."
- reference: PMID:12207163
  title: "Molecular and cellular basis of isolated dominant-negative growth hormone deficiency, IGHD type II: insights on the secretory pathway of peptide hormones."
- reference: PMID:9432120
  title: "Prevalence of human GH-1 gene alterations in patients with isolated growth hormone deficiency."
- reference: PMID:9814493
  title: "Phenotype and genetic analysis of a syndrome caused by an inactivating mutation in the growth hormone-releasing hormone receptor: Dwarfism of Sindh."
- reference: PMID:17073157
  title: "GH-1 gene splicing mutations: molecular basis of hereditary isolated growth hormone deficiency in children."
- reference: PMID:12720086
  title: "Disruption of exon definition produces a dominant-negative growth hormone isoform that causes somatotroph death and IGHD II."
- reference: PMID:23736291
  title: "Endoplasmic reticulum stress and apoptosis contribute to the pathogenesis of dominantly inherited isolated GH deficiency due to GH1 gene splice site mutations."
- reference: PMID:7650402
  title: "Molecular genetic analysis of X-linked hypogammaglobulinemia and isolated growth hormone deficiency."
- reference: PMID:7959728
  title: "Isolation of cosmid and cDNA clones in the region surrounding the BTK gene at Xq21.3-q22."
- reference: PMID:15800844
  title: "Over- and underdosage of SOX3 is associated with infundibular hypoplasia and hypopituitarism."
- reference: DOI:10.3390/endocrines5030025
  title: "Isolated Growth Hormone Deficiency"
- reference: PMID:36960394
  title: "A GHRHR founder mutation causes isolated growth hormone deficiency type IV in a consanguineous Pakistani family."
- reference: PMID:31707392
  title: "GHD Diagnostics in Europe and the US: An Audit of National Guidelines and Practice."
- reference: PMID:9802480
  title: "MR imaging in idiopathic growth hormone deficiency."
- reference: clinicaltrials:NCT03831880
  title: "A PHASE 3, RANDOMIZED, MULTICENTER, OPEN-LABEL, CROSSOVER STUDY ASSESSING SUBJECT PERCEPTION OF TREATMENT BURDEN WITH USE OF WEEKLY GROWTH HORMONE (SOMATROGON) VERSUS DAILY GROWTH HORMONE (GENOTROPIN (REGISTERED)) INJECTIONS IN CHILDREN WITH GROWTH HORMONE DEFICIENCY"
- reference: clinicaltrials:NCT04513171
  title: "A Multi-center, Randomized, Positive-control, Phase 2&3 Combined Study of Y-shape Pegylated Somatropin in Prepubertal Children With Growth Hormone Deficiency."
- reference: clinicaltrials:NCT04786873
  title: "Multicenter, Open Label Trial to Investigate the Efficacy and Safety of a Single Oral Dose of 1.0 mg/kg Macimorelin Acetate as Growth Hormone Stimulation Test (GHST) in Pediatric Patients With Suspected Growth Hormone Deficiency (GHD)"
- reference: clinicaltrials:NCT04614337
  title: "A Multicenter, 24-Month, Randomized, Open-Label, Active Control, Parallel Arm, Phase 2 Study of Daily Oral LUM-201 in Naïve-to-Treatment, Prepubertal Children With Idiopathic Growth Hormone Deficiency (GHD)"
- reference: clinicaltrials:NCT04806854
  title: "A Single-Center, Randomized, Open-Label, Parallel Arm Study of Daily Oral LUM-201 in Naive-to-Treatment, Prepubertal Children With Idiopathic Pediatric Growth Hormone Deficiency (PGHD)"

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