Scientific Reference
Somatropin (HGH 191aa)
Evidence profile: Human Phase 3 evidence
Somatropin is human growth hormone produced by recombinant methods: one chain of 191 amino acids matching the main form of the hormone made by the pituitary. The chain folds into a bundle of four alpha-helices cross-braced by two disulphide bridges, giving a mass near 22 kDa; a shorter 20 kDa variant formed by alternative splicing also circulates naturally. Growth hormone sits in a structural family with prolactin and placental lactogen, and the human hormone can engage the prolactin receptor as well as its own. After decades of study in people, animals and cell systems, the open questions are mostly about signalling detail and tissue-specific actions, much of it still in cell and rodent models.
Mechanism of Action
The hormone binds the growth hormone receptor, a class I cytokine receptor present on the cell surface as a pre-formed dimer. A single hormone molecule contacts two receptor chains through two different binding sites, and the resulting conformational change activates the tyrosine kinase JAK2. JAK2 phosphorylates the receptor and the transcription factor STAT5, and MAPK and PI3K signalling have also been described. In the liver STAT5 drives transcription of the IGF-1 gene, which is why many effects seen in animals are credited jointly to growth hormone and IGF-1. SOCS proteins, induced by the same pathway, dampen the signal.
Molecular Information
- Type: Single-chain polypeptide hormone
Pharmacokinetics
The mean terminal half-life of intravenous GENOTROPIN in normal adults is 0.4 hours, whereas subcutaneously administered GENOTROPIN has a half-life of 3.0 hours in GHD adults. The observed difference is due to slow absorption from the su… The bioavailability of subcutaneously administered somatropin is approximately 80% in both healthy subjects and growth hormone deficient patients. A subcutaneous dose of 5 mg of Omnitrope 5 mg/1.5 ml solution for injection in healthy adu…
Published Research
Efficacy and Safety of Weekly Somatrogon vs Daily Somatropin in Children With Growth Hormone Deficiency: A Phase 3 Study
Deal CL et al. · The Journal of clinical endocrinology and metabolism · 2022 · Clinical
PMID 35405011 — View on PubMedWeekly Lonapegsomatropin in Treatment-Naïve Children With Growth Hormone Deficiency: The Phase 3 heiGHt Trial
Thornton PS et al. · The Journal of clinical endocrinology and metabolism · 2021 · Clinical
PMID 34272849 — View on PubMedComparison between long-acting pegylated and daily recombinant human growth hormone for pediatric growth hormone deficiency a systematic review
Zhang J et al. · Scientific reports · 2025 · Review
PMID 40702077 — View on PubMedGlobal trends in recombinant human growth hormone for the treatment of idiopathic short stature: a bibliometric analysis
Ouyang R et al. · Frontiers in medicine · 2025 · Review
PMID 40842547 — View on PubMedRecombinant human growth hormone for children born small for gestational age: meta-analysis confirms the consistent dose-effect relationship on catch-up growth
Crabbé R et al. · Journal of endocrinological investigation · 2008 · Review
PMID 18475054 — View on PubMed