| Domain/subtype | Key gene or feature | Inheritance/mechanism | Defining phenotype/diagnostic clue | Suggested ontology terms | Evidence note |
|---|---|---|---|---|---|
| Disease entity | Isolated growth hormone deficiency (IGHD) | Pituitary GH deficiency occurring as congenital/genetic, acquired, or idiopathic isolated deficiency | Short stature, reduced growth velocity, delayed bone age; neonatal cases may show hypoglycemia/jaundice/micropenis | MONDO: isolated congenital growth hormone deficiency (MONDO_0000050); HPO: Short stature, Delayed bone age, Hypoglycemia, Micropenis; UBERON: pituitary gland, hypothalamus | Incidence ~1:4,000-10,000 live births; most cases idiopathic; familial 3-30% (pqac-00000005, pqac-00000010, pqac-00000011) |
| IGHD IA | **GH1** | Autosomal recessive; usually homozygous GH1 deletion/null variants causing absent GH production | Early severe short stature, often height < -4.5 SDS; undetectable GH; anti-GH antibodies/tachyphylaxis may occur with therapy | MONDO: isolated growth hormone deficiency type IA (MONDO_0009876); HPO: Short stature, Growth delay; GO: growth hormone secretion; CL: somatotroph; UBERON: anterior pituitary gland | 6.7 kb GH1 deletion reported as most frequent classic lesion; severe phenotype emphasized across reviews (pqac-00000004, pqac-00000013) |
| IGHD IB | **GH1** | Autosomal recessive; biallelic nonsense/frameshift/splice variants with residual GH | Milder growth failure than IA; low but detectable GH; generally good response to rhGH | MONDO: isolated growth hormone deficiency type IB (MONDO_0013006); HPO: Short stature, Delayed bone age; CL: somatotroph | Novel homozygous GH1 p.Tyr54* reported in 2023 cohort; immune tolerance better than IA (pqac-00000006, pqac-00000008) |
| IGHD II | **GH1** | Autosomal dominant; often splice-site or exon 3-skipping/dominant-negative mechanism | Variable short stature with low but detectable GH and low IGF-1; may progress to MPHD; MRI often normal or anterior pituitary hypoplasia | MONDO: isolated growth hormone deficiency type II (MONDO_0008250); HPO: Short stature, Delayed bone age, Pituitary hypoplasia; GO: mRNA splicing, growth hormone secretion; CL: somatotroph | 2024 Chinese series: mean age 4.64 y, mean height -3.95 SDS, peak GH 2.83 ng/mL; first-year height gain 1.79 SDS on rhGH (pqac-00000007, pqac-00000019) |
| IGHD III | **SOX3** or **BTK** | X-linked; developmental pituitary defects or BTK-related exon skipping with immune phenotype | IGHD or MPHD, sometimes ectopic posterior pituitary, intellectual disability, abnormal immune function/agammaglobulinemia | HPO: Short stature, Agammaglobulinemia, Intellectual disability, Ectopic posterior pituitary; UBERON: posterior pituitary gland | X-linked form recognized in current review; may not remain purely isolated clinically (pqac-00000013, pqac-00000009) |
| IGHD IV | **GHRHR** | Autosomal recessive; impaired GHRH receptor signaling in somatotrophs | Pituitary hypoplasia, severe short stature, very low baseline/stimulated GH, low IGF-1/IGFBP-3; good response to rhGH | HPO: Pituitary hypoplasia, Short stature; GO: G protein-coupled receptor signaling pathway, growth hormone secretion; CL: somatotroph | Includes classic c.57+1G>A and other receptor-defect mechanisms; little/lit mouse is homologous mechanistic model (pqac-00000004, pqac-00000013, pqac-00000044) |
| IGHD V | **RNPC3** | Autosomal recessive; defective minor spliceosome mRNA processing | Severe postnatal growth retardation, undetectable GH, low/undetectable IGF-1 and IGFBP-3, anterior pituitary hypoplasia; females may develop ovarian insufficiency | HPO: Postnatal growth retardation, Pituitary hypoplasia, Ovarian insufficiency; GO: mRNA splicing, via spliceosome; UBERON: anterior pituitary gland | RNPC3 is an established disease gene in MONDO_0000050 resources and reviews (pqac-00000000, pqac-00000013) |
| Other rare genetic cause | **GHSR** | AD or AR loss-of-function affecting ghrelin receptor activity | Familial short stature/partial IGHD with low GH responses | HPO: Short stature; GO: ghrelin receptor signaling pathway, regulation of growth hormone secretion | 2024 Egyptian series found pathogenic **GHRHR** p.Arg357Cys in one case and novel **GHSR** c.1043dup p.Ser349Leufs*6 in another; 90% underweight, 50% anemia, 80% hypovitaminosis D in the 10-patient cohort (pqac-00000035) |
| Broader pituitary-development genes | **PROP1, HESX1, SOX3, OTX2, GLI2, LHX3, LHX4, POU1F1** | Mostly developmental transcription-factor defects; usually MPHD spectrum but can present as isolated GHD | Extreme short stature, family history, or structural pituitary anomalies prompt testing beyond GH1/GHRHR | GO: pituitary gland development; CL: pituitary endocrine cell; UBERON: pituitary gland | These genes are important differential/extended panel targets rather than core isolated-disease genes (pqac-00000005, pqac-00000038) |
| Core diagnostics | Auxology + biochemistry + dynamic testing | Diagnostic process integrates phenotype, IGF-1/IGFBP-3, GH stimulation tests, and MRI | Height < -2 SDS; reduced height velocity; delayed bone age; classic approach uses inadequate response to 2 GH stimulation tests | HPO: Short stature, Delayed bone age; UBERON: pituitary gland; term: growth hormone stimulation test | GHST cutoffs remain assay/test dependent and vary ~3-10 µg/L across centers; recent guidelines still recommend GHST in most children (pqac-00000011, pqac-00000039, pqac-00000042) |
| Diagnostic confounders | BMI, puberty, assay variability | Obesity lowers peak stimulated GH; puberty status affects interpretation; sex-steroid priming reduces false positives | Consider priming in prepubertal boys >11 y and girls >10 y; interpret low IGF-1 in context | term: body mass index; HPO: Delayed puberty | Meta-analysis of 58 studies (n=5,135): each 1-point BMI SDS increase lowered peak GH by 11.6%; proposed lower BMI-adjusted cutoffs (pqac-00000033) |
| MRI/anatomy | Pituitary MRI | Structural assessment of hypothalamic-pituitary region after biochemical diagnosis | Pituitary hypoplasia most common; also PSIS and ectopic posterior pituitary; normal MRI does not exclude genetic IGHD | HPO: Pituitary hypoplasia, Ectopic posterior pituitary, Pituitary stalk interruption syndrome; UBERON: hypothalamus, pituitary stalk | MRI is recommended after confirmation; reduced pituitary volume alone is not diagnostic (pqac-00000013, pqac-00000042) |
| Genetic testing workflow | Panel/MLPA/WES | Start with targeted testing when family history, extreme short stature, or anatomical anomalies; MLPA useful for deletions/duplications | Useful especially for **GH1**, **GHRHR**, **GHSR**, and extended pituitary-development genes | term: next-generation sequencing panel; term: MLPA; term: whole exome sequencing | 25-gene panel with 99.2% coverage used in 2023 GH1 cohort; genetic testing specifically indicated by current review in familial/anatomic/extreme cases (pqac-00000038, pqac-00000013) |
| Daily standard therapy | Somatropin (rhGH) | Replacement therapy restoring GH action and IGF-1 generation | Improves short-term height gain, adult height, body composition; monitor IGF-1, thyroid/adrenal function, headaches/SCFE | NCIT: Somatropin; GO: JAK-STAT cascade involved in growth hormone signaling pathway | Suggested starting dose 22-35 µg/kg/day (0.16-0.24 mg/kg/week); first-year response and adherence predict outcome (pqac-00000016, pqac-00000002) |
| Weekly long-acting GH | Somatrogon, somapacitan, lonapegsomatropin; also Jintrolong, Eutropin Plus in specific markets | Extended half-life/fusion, albumin-binding, prodrug, or PEGylated formulations | Less injection burden; efficacy and safety generally non-inferior to daily GH in pediatric GHD | NCIT terms if available not asserted; term: long-acting growth hormone replacement | Current review lists approvals since 2021 for somatrogon/somapacitan/lonapegsomatropin; same efficacy/safety as daily hGH in cited trials/reviews (pqac-00000017, pqac-00000026) |
| Emerging therapy | LUM-201 (ibutamoren analog/oral GH secretagogue program) | Oral GH secretagogue strategy requiring residual pituitary function; not replacement | Trials enroll idiopathic pediatric GHD with delayed bone age and partial GH reserve rather than severe absent pituitary function | term: growth hormone secretagogue | OraGrowtH210 (NCT04614337) randomized 104 children; OraGrowtH212 (NCT04806854) active, PK/PD, estimated n=24; excludes maximal stimulated GH ≤3 ng/mL/organic disease (pqac-00000034, pqac-00000030) |
| Emerging diagnostic tool | Macimorelin GH stimulation test | Oral ghrelin agonist as diagnostic GHST | Pediatric phase 3 evaluates diagnostic accuracy/repeatability against clonidine and arginine | term: Macimorelin; term: growth hormone stimulation test | DETECT trial NCT04786873 completed in 2024, actual enrollment 101, crossover diagnostic design (pqac-00000032) |
| Key mechanisms | Hypothalamic GHRH/somatostatin; pituitary somatotroph; hepatic IGF-1 axis | Upstream hypothalamic control -> pituitary GH secretion -> GHR/JAK2/STAT5B signaling -> IGF1/IGFBP3/ALS -> growth plate and metabolic effects | Mechanistically explains linear growth failure, altered body composition, and low IGF-1 | GO: growth hormone secretion; GO: JAK-STAT cascade involved in growth hormone signaling pathway; CL: somatotroph; UBERON: liver, growth plate | Mechanistic chain supported by recent reviews and classic models including little mouse and GH1 splicing models (pqac-00000020, pqac-00000021, pqac-00000022, pqac-00000044) |


*Table: This compact table summarizes isolated growth hormone deficiency subtypes, core diagnostics, treatments, and mechanistic annotations for structured knowledge-base use. It prioritizes supported identifiers and recent evidence, including 2023-2024 cohorts and active/emerging clinical applications.*