Epidemiology & Classification
- Pediatric GHD: Incidence ~1:4,000–1:10,000 live births. Classified as:
- Congenital: Present at birth; often idiopathic (75%) or associated with structural CNS anomalies (e.g., septo-optic dysplasia), genetic mutations (e.g., GH1, GHRHR, POU1F1, HESX1), or syndromes (Prader-Willi, Turner, SHOX deficiency).
- Acquired: Secondary to CNS radiation (>90% develop hypopituitarism after cranial RT ≥18 Gy), tumors (craniopharyngioma most common), trauma, infection (e.g., TB, meningitis), or infiltrative diseases (Langerhans cell histiocytosis—LCH; sarcoidosis).
- Adult-onset GHD (AO-GHD): Primarily acquired (~90% due to pituitary adenomas ± surgery/radiotherapy). Incidence ~2–3 cases per 100,000 adults/year. Idiopathic AO-GHD is rare (<10% of cases).
Key update (ES临床指南 2023, J Clin Endocrinol Metab): New data confirm transient GHD post-pituitary surgery in up to 30% of patients; hence, repeat testing at ≥3 months is mandatory before diagnosing permanent deficiency.
Pathophysiology & Etiology
A. In Children
| Category | Examples | Clinical Relevance |
|---|---|---|
| Genetic | GH1 (autosomal recessive), GHRHR (Dutch-type), PROP1 (most common familial cause; associated with delayed hormone deficiencies) | Screen for PROP1 in pediatric GHD + delayed pubertal progression or panhypopituitarism |
| Structural | Septo-optic dysplasia (SOD), midline defects (cleft palate, holoprosencephaly), empty sella | SOD: 30–50% develop GHD; optic nerve hypoplasia may be subtle—screen with ophthalmology referral |
| Acquired | Craniopharyngioma (50–70% develop GHD post-resection), LCH (bone lesions ± hypothalamic involvement), CNS infections | LCH: Lytic skull lesions + diabetes insipidus strongly suggests hypothalamic-pituitary involvement |
Critical nuance: Subtotal cranial radiotherapy (≥15 Gy) causes progressive GHD over 2–5 years due to stem cell depletion in anterior pituitary. Growth velocity decline often precedes IGF-1 suppression.
B. In Adults
| Etiology | Mechanism | Prevalence in AO-GHD |
|---|---|---|
| Pituitary adenoma (functional/non-functioning) | Mass effect + stalk disruption + post-resection damage | ~80% of cases |
| Radiotherapy | Endothelial injury → fibrosis → progressive pituitary failure | 50–75% develop GHD at 10 years post-RT |
| Traumatic brain injury (TBI) | Axonal shearing of pituitary stalk | 15–30% in severe TBI (GCS <8); often underdiagnosed |
| Sheehan’s syndrome / Pituitary apoplexy | Ischemic necrosis | Apoplexy: 30–60% develop acute panhypopituitarism |
Evidence: A 2023 meta-analysis (Eur J Endocrinol) confirmed GHD prevalence in LCH is 41%—higher than previously reported.
Clinical Manifestations
Children
- Growth failure: Height velocity <5 cm/year (preschool), <6 cm/year (pubertal prepubertal), or >2 SD below mean for bone age. Not synonymous with short stature—some children maintain height on growth curve but have reduced growth velocity.
- Biochemical red flags:
- Neonatal hypoglycemia (especially if prolonged)
- Micropenis (<2.5 cm stretched length) in males
- Delayed dentition, high-pitched voice, immature facies
- Syndromic features:
- Prader-Willi: Hyperphagia, obesity, hypotonia
- Turner: Webbed neck, lymphedema, coarctation
Diagnostic pitfall: Idiopathic GHD may present with normal birth length—growth faltering emerges by age 2–3 years.
Adults
- Body composition: ↑ visceral fat (↑ waist circumference), ↓ lean body mass (↓ grip strength correlates with GH dose)
- Cardiovascular: Dyslipidemia (↑ LDL, ↓ HDL), endothelial dysfunction → ↑ carotid IMT
- Metabolic: Insulin resistance (HOMA-IR ↑ 20–30% untreated); ↑ fracture risk (vertebral fractures OR 2.5×)
- Quality of life: fatigue (85% of cases), depression (HAM-D score ↑), impaired concentration (QoL-AGHDA questionnaire validated in clinical practice)
Key update: GHD adults have 1.5–2× higher cardiovascular mortality vs. matched controls (JCEM 2022 cohort study, n=1,842).
Diagnostic Evaluation
A. Screening Tests
- First-line:
- IGF-1: Age-adjusted SD score (critical—levels decline with aging, obesity, diabetes). Use assay-specific reference ranges.
- IGFBP-3: Complementary marker, especially in children <2 years where IGF-1 is less reliable.
B. Dynamic Testing (Gold Standard for GHD Confirmation)
Indicated if IGF-1 is borderline/low-normal or when diagnosis is uncertain.
| Stimulant | Cutoff for GHD* | Sensitivity | Specificity |
|---|---|---|---|
| Insulin Tolerance Test (ITT) | GH peak <3 µg/L | 90% | 95% |
| Glucagon stimulation test (GST) | GH peak <3.1 µg/L | 85% | 92% |
| Arginine + GHRH-49 | GH peak <6.2 µg/L | 88% | 90% |
Critical updates (ES consensus 2023):
- ITT remains gold standard but contraindicated in seizures, CAD, or elderly.
- GST preferred for adults: safer, comparable accuracy, no insulin-induced hypoglycemia risk.
- In children: Arginine + GHRH is first-line; ITT only if high suspicion and no contraindications.
C. Imaging & Pituitary Workup
- MRI pituitary (with contrast) for all new-onset GHD—essential to rule out tumor/stalk abnormalities.
- Visual field testing if suprasellar mass suspected.
- Bone age X-ray (left hand/wrist) in children: Delayed ossification supports GHD.
Caution: IGF-1 can be falsely low in malnutrition, liver disease, or uncontrolled diabetes—exclude these before diagnosing GHD.
Treatment Principles
A. GH Replacement in Adults
- Indications (per FDA/EMA & ES guidelines):
- Confirmed severe GHD (peak GH <3–5 µg/L on stimulation)
- Absent pituitary function (panhypopituitarism with low free T4, cortisol, gonadotropins, and IGF-1)
- Not indicated for age-related decline without biochemical GHD.
- Dosing:
- Start low: 0.2–0.3 mg/day (recombinant human GH, e.g., somatropin)
- Titrate by:
- IGF-1 levels (target mid-normal range for age/sex)
- Clinical response (waist circumference, body composition via DXA)
- Side effects
- Max dose: ≤1.0 mg/day (women often require higher mg/kg than men due to estrogen-induced GH resistance).
B. Monitoring & Safety
| Parameter | Frequency | Clinical Action |
|---|---|---|
| IGF-1 | Every 3 months, then 6–12 months once stable | Adjust dose if >2 SD above mean (risk of acromegaly) or <−2 SD (under-replacement) |
| Glucose metabolism | Fasting glucose/HbA1c at baseline & q6mo | ↑ Diabetes risk—screen annually; adjust insulin if T2DM present |
| Carpal tunnel | Clinical exam at each visit | Discontinue GH if symptoms severe (decompression may be needed) |
| Pituitary tumor | MRI q6–12mo in patients with residual tumor | No evidence of GH promoting adenoma growth per SWOG S0822 trial (2023 update) |
Contraindications (per FDA):
- Active malignancy (excluding successfully treated non-melanoma skin cancer)
- Closed epiphyses in pediatric patients (unless for Turner/SHOX deficiency—off-label use)
- Critical illness post-op (e.g., cardiac surgery, major trauma)—↑ mortality risk (NEJM 2013)
C. Pediatric Management
- Goal: Achieve adult height within genetic potential (mid-parental height ± 8.5 cm).
- Dosing: 0.16–0.24 mg/kg/week (divided daily injections).
- Monitoring:
- Height velocity q3mo
- Bone age q6–12mo
- T4, IGF-1 baseline + annually
- Transition to adult care: Re-test GH function at ≥5 years post-puberty completion—~30% recover spontaneous GH secretion.
Controversy: Use of high-dose GH in idiopathic short stature (ISS)—FDA-approved but controversial; benefits modest (↑ height by 2–7 cm) with long-term safety concerns. EMA does not approve for ISS.
Prognosis & Long-Term Outcomes
- Children: With early GH therapy, 80% achieve adult height >−2 SD. Delayed diagnosis (>2 years from symptom onset) reduces final height by 5–10 cm.
- Adults: GH replacement:
- ↓ visceral fat by 10–15% within 6 months
- ↑ bone mineral density by 3–8% over 2 years (vertebral fractures ↓)
- Improves QoL scores within 3–6 months
Long-term data (KIMS database, n=15,000): GH therapy normalizes cardiovascular mortality to population levels after 5+ years of treatment.
Key Takeaways for Clinicians
- Suspect GHD in unexplained short stature + hypoglycemia (children) or metabolic syndrome + low energy (adults).
- Confirm diagnosis with dynamic testing—do not rely on single IGF-1.
- In adults: Start low-dose GH, titrate to IGF-1 and clinical response; monitor for glucose intolerance.
- Screen all pituitary tumor patients annually for GHD—even if asymptomatic.
- Avoid GH in active cancer or critical illness—reassess after recovery.
