What it is
Somatropin is human growth hormone made by recombinant DNA technology. UniProt's record for the hormone (P01241, somatotropin) gives a 217-residue precursor: a 26-residue signal sequence, then the 191-amino-acid hormone, held by two disulfide bonds. The Norditropin label describes the drug the same way — 191 amino acids, about 22,000 daltons, made in E. coli, with "the amino acid sequence … identical to that of human growth hormone of pituitary origin."
At 191 residues, growth hormone is a protein, nearly five times the 40-residue line in 21 CFR 600.3. It is in this library because readers search for it among peptides — largely because the peptides that make the pituitary release it (sermorelin, tesamorelin, ipamorelin) are sold and discussed alongside it. Its nearest relative by structure is prolactin: UniProt places both in the somatotropin/prolactin family.
What it does
UniProt's function annotation: growth hormone "plays an important role in growth control. Its major role in stimulating body growth is to stimulate the liver and other tissues to secrete IGF1." It also stimulates the differentiation and proliferation of muscle-precursor cells and amino-acid uptake and protein synthesis in muscle and other tissues. So much of what growth hormone does, it does through IGF-1. The library's entries on ghrelin, sermorelin and somatostatin cover the signals that raise and lower its release.
From pituitary extracts to bacteria
Before recombinant somatropin, growth hormone for treatment was extracted from human pituitary glands. In the United States it was distributed through the National Hormone and Pituitary Program, and its recipients turned out to be at risk of Creutzfeldt-Jakob disease:
| Study | Cohort | Finding |
|---|---|---|
| Fradkin et al., JAMA 1991 (PMID 1992185) | 6,284 US recipients | 7 confirmed CJD cases, all among the ~700 who started before 1970; longer treatment was a major risk factor |
| Mills et al., J Pediatr 2004 (PMID 15069388) | 6,107 people treated 1963–1985 | 26 CJD cases; deaths 433 vs 114 expected, mostly from the underlying conditions (adrenal insufficiency, low blood sugar) rather than CJD |
The Mills authors' summary is precise: replacing pituitary-derived growth hormone with recombinant hormone "eliminated only the risk of Creutzfeldt-Jakob disease."
The approved products
openFDA's Drugs@FDA dataset lists five somatropin applications (read 2026-10-20):
| Brand | Holder | Application |
|---|---|---|
| Humatrope | Eli Lilly | BLA 019640 |
| Zomacton | Ferring | BLA 019774 |
| Genotropin | Pfizer | BLA 020280 |
| Norditropin | Novo Nordisk | BLA 021148 |
| Omnitrope | Sandoz | BLA 021426 |
The Norditropin label's indications illustrate the class: in children, growth failure from inadequate growth hormone secretion, and short stature with Noonan syndrome, Turner syndrome, small for gestational age without catch-up growth by age 2 to 4, idiopathic short stature, and growth failure from Prader-Willi syndrome; in adults, replacement in growth hormone deficiency. Indications differ slightly by brand; each label is the authority for its own product.
Three long-acting versions now carry their own US labels, each a different engineering answer to daily injections:
| Product | What was changed | Label |
|---|---|---|
| Skytrofa (lonapegsomatropin) | Somatropin attached to methoxypolyethylene glycol carriers by a releasable linker; 63 kDa, releasing 22 kDa somatropin | BLA 761177 |
| Sogroya (somapacitan) | One amino-acid substitution (L101C) carrying an albumin-binding side chain; protein part 191 residues | BLA 761156 |
| Ngenla (somatrogon) | Fused to C-terminal peptides from the beta chain of hCG; about 40 kDa, made in hamster cells | BLA 761184 |
The same releasable-carrier idea holds a much smaller peptide in Yorvipath, a slow-release form of PTH(1-34); a drug whose polyethylene glycol stays attached for good is the complement blocker Empaveli/Syfovre.
The drug that does the opposite — blocks the growth hormone receptor in acromegaly — is pegvisomant (Somavert), also a 191-residue growth hormone analogue, per its label.
Where it stands
- United States: a prescription biologic, approved for the uses on each label.
- The distribution law. Growth hormone has its own clause in federal food and drug law: under 21 U.S.C. 333(e), knowingly distributing — or possessing with intent to distribute — human growth hormone "for any use in humans other than the treatment of a disease or other recognized medical condition" authorised by FDA and ordered by a physician is punishable by up to 5 years in prison, or 10 if the offence involves a person under 18. Anti-ageing and bodybuilding are not authorised uses.
- Published record: PubMed returns 54,660 records for somatropin or human growth hormone, 2,502 tagged as randomised controlled trials; ClinicalTrials.gov lists 818 studies with somatropin as an intervention (2026-10-20).
Related reading
IGF-1 carries much of growth hormone's effect; sermorelin and tesamorelin are GHRH analogues that make the pituitary release it; somatostatin switches it off.