Somatropin is recombinant 191-amino-acid human growth hormone. Approved products replace deficient growth hormone in defined paediatric and adult conditions; this is the reference molecule against which secretagogues and modified growth-hormone fragments should be understood.

Established. Review the research and limitations before relying on this record.

Somatropin is sequence-identical to the predominant endogenous 22 kDa human growth hormone. Binding to the growth-hormone receptor activates JAK2-STAT signalling and induces hepatic and local IGF-1 production. It also directly affects protein, carbohydrate and lipid metabolism. This is receptor replacement, unlike CJC-1295, sermorelin and the GHRPs, which try to stimulate endogenous release.

The Genotropin label reports approximately 80% subcutaneous bioavailability in adults with growth hormone deficiency, a mean time to peak near six hours, and a mean subcutaneous terminal half-life of about three hours. Protein catabolism occurs principally in liver and kidney. Product formulation and patient population can change these values.

FDA-approved somatropin products have formulation-specific labels covering growth hormone deficiency and selected causes of paediatric growth failure. Genotropin was compared with placebo in six randomised adult growth-hormone-deficiency trials totalling 172 participants; treatment increased lean mass and reduced fat mass and waist circumference. Those findings are replacement-therapy evidence in diagnosed deficiency, not evidence for anti-ageing, bodybuilding or use by people with normal growth-hormone function.

The FDA label contraindicates use in acute critical illness, active malignancy, active proliferative or severe non-proliferative diabetic retinopathy, and for growth promotion after epiphyseal closure. Important risks include reduced insulin sensitivity, fluid retention, intracranial hypertension, severe hypersensitivity, unmasking of hypoadrenalism or hypothyroidism, and slipped capital femoral epiphysis in children. Pharmacologic doses increased mortality in critically ill adults in two trials.

This is a source-backed summary, not a recommendation. Read the mechanism, pharmacokinetic, human-evidence and reported-effect fields separately: a mechanism is not an outcome. Availability, legal status and product quality differ by jurisdiction; consult a qualified clinician.