Scientific Reference
HGH (Somatropin, 191aa)
Evidence profile: Human Phase 3 evidence
Somatropin is recombinant human growth hormone, a single chain of 191 amino acids with the same sequence as the main pituitary form of the hormone. The chain folds into a bundle of four alpha-helices held by two disulphide bridges, giving a mass of about 22 kDa; a shorter 20 kDa variant, made by alternative splicing, also circulates naturally. Growth hormone belongs to a structural family with prolactin and placental lactogen, and the human hormone can bind the prolactin receptor as well as its own. Its physiology has been studied for decades in people, animals and cell systems. Open questions now sit mostly in signalling detail and tissue-specific actions, where much of the work is still in cell and rodent models.
Mechanism of Action
Growth hormone binds the growth hormone receptor, a class I cytokine receptor that sits on the cell surface as a pre-formed dimer. One hormone molecule engages two receptor chains through two distinct binding sites, and the conformational change that follows activates the associated tyrosine kinase JAK2. JAK2 phosphorylates the receptor and the transcription factor STAT5; signalling through the MAPK and PI3K pathways has also been described. In the liver, STAT5 drives transcription of the IGF-1 gene, so many actions studied in animals are attributed jointly to growth hormone and IGF-1. SOCS proteins, induced by the same pathway, damp the signal.
Molecular Information
- Type: Single-chain polypeptide hormone
- Length: 191 amino acids
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