What it is
Growth hormone is made by the pituitary gland. This is a pea-sized gland under the brain. In children, it makes them grow taller. In adults, it helps control body fat, muscle, bone and blood sugar. Much of its work is done through a second hormone, called IGF-1. When growth hormone goes up, the body makes more IGF-1. It is made mostly in the liver.
Somatropin is the lab-made version of growth hormone. It has exactly the same 191 building blocks as the natural hormone. It is made by bacteria or grown cells that carry the human gene. It is a prescription medicine sold under several brand names. It is injected under the skin, usually every day.
Three newer products are taken once a week: Sogroya, Skytrofa and Ngenla. They are related, but they are different chemicals. They are described below only for comparison.
Somatropin is a non-glycosylated, single-chain 191-residue protein (22,124 Da per the Genotropin label) with a sequence identical to pituitary hGH. It binds the growth hormone receptor, a cytokine-family receptor that signals through JAK2 and STAT5, stimulating hepatic IGF-1 synthesis and exerting direct effects: lipolysis, nitrogen retention, sodium and phosphate retention, and reduced insulin sensitivity. It also inhibits 11β-HSD1, which can unmask central adrenal insufficiency.
Genotropin label pharmacokinetics in adults with GH deficiency: subcutaneous bioavailability about 80%, Tmax about 6 hours, apparent clearance 0.3 L/h/kg, volume 1.3 L/kg, terminal half-life 3.0 hours subcutaneously versus 0.4 hours intravenously, the difference reflecting slow absorption. Clearance is by proteolysis in liver and kidney.
The weekly products differ structurally: somapacitan carries an L101C substitution with an albumin-binding side chain; lonapegsomatropin is somatropin transiently linked to a 4 × 10 kDa methoxy-PEG carrier and releases unmodified somatropin; somatrogon fuses hGH to C-terminal peptides from the hCG β chain.
Who made it and when
From 1963 to 1985, some American children did not make enough growth hormone. They were treated with hormone taken from the pituitary glands of people who had died. A government program supplied it. In 1985, three young men treated this way died of Creutzfeldt-Jakob disease. This is a deadly brain disease caused by infectious proteins. The program stopped handing out the hormone right away. Nearly 7,700 people in the US got this hormone. As of November 2020, 36 of them had developed the disease.
A lab-made replacement came the same year. In 1979, the company Genentech showed that bacteria could make the hormone. Its product, Protropin, was approved in October 1985. Protropin had one extra building block. Lilly’s Humatrope was approved in 1987. It matched the natural hormone exactly. Several more brands followed, up to 2006.
The NIH-funded National Hormone and Pituitary Program distributed cadaveric pituitary hGH from 1963 to 1985. HHS halted distribution in 1985 after three recipients died of CJD; it has identified 36 cases among nearly 7,700 US recipients, none among patients who began treatment after 1977, when an additional purification step was introduced.
Goeddel et al. (Nature 1979) expressed a hybrid synthetic/cDNA hGH gene in E. coli. Genentech’s Protropin (somatrem, methionyl-hGH, 192 residues) was approved on 18 October 1985 as the company’s first product and ceased production in 2004. FDA’s 2020 list of deemed biologics licences gives initial approval dates for the somatropin applications: Humatrope 1987, Nutropin 1993, Zomacton 1995, Genotropin 1995, Serostim and Saizen 1996, Norditropin (current application) 2000 and Omnitrope 2006. Genentech discontinued all Nutropin AQ NuSpin formulations in the US on 31 December 2024 for business reasons. The weekly analogues followed: Sogroya (adults 2020, with pediatric indications added through February 2026), Skytrofa (children 2021, adults 2025) and Ngenla (children 2023).
What the data say
Growth hormone has been tested for the uses on its label. In those trials, children grew more. Adults with a proven lack of growth hormone had less body fat and more lean mass (muscle and other non-fat tissue). Outside those uses, there are few well-controlled studies.
A small 1990 study looked at older men. It reported more lean mass and less fat after six months. Later, growth hormone was widely sold as an “anti-aging” treatment. The FDA has never approved it for this use. Larger trials in older adults found small changes in body shape. But people gained little or no strength. Side effects were common. They included swelling, joint pain and carpal tunnel syndrome (numb, tingling hands). They also included new diabetes or high blood sugar. In people who play sports for fun, sprint speed went up a little. It went back down after they stopped. In very sick patients in intensive care, high doses about doubled the death rate.
Rudman et al. (NEJM 1990; 12 treated, 9 untreated men aged 61–81) reported lean body mass +8.8% and adipose mass −14.4% after 0.03 mg/kg three times weekly for six months. In the NIA trial (Blackman et al., JAMA 2002; n=131, 26 weeks), GH alone increased lean mass by 3.1 kg in men and 1.0 kg in women; strength did not rise significantly, edema affected 39% of women and arthralgia 41% of men on GH, and diabetes or glucose intolerance occurred in 18 GH-treated men versus 7. A systematic review of 18 study populations (220 GH-treated participants) found fat mass −2.1 kg and lean mass +2.1 kg with unchanged weight, more edema, arthralgia, carpal tunnel syndrome and gynaecomastia, and concluded that the evidence did not support GH as an anti-ageing therapy (Liu et al., 2007).
Meinhardt et al. (2010; n=96) found sprint capacity +3.9% after 2 mg/day for eight weeks, with no change in endurance, strength or power. Takala et al. (1999; n=532) reported in-hospital mortality of 39% versus 20% and 44% versus 18% in critically ill adults. FDA judged the French SAGhE mortality signal inconclusive in 2011.
Regulatory picture
Approval: somatropin is fully approved by the FDA. But it is approved only for the uses on each brand’s label. These are: children who do not grow well because they lack growth hormone, children with some genetic or birth-related growth conditions, and adults who lack growth hormone. One brand, Serostim, is also approved for adults with HIV who are losing a lot of weight and muscle.
Compounding: since March 2020, somatropin has been treated as a biological product (a medicine made from living cells). Pharmacies may not make their own copies of it.
Selling and sharing: federal law limits handing out this drug for other uses, which is unusual. Since 1990, it has been a serious crime (a felony) to give out growth hormone for other uses. Holding it and planning to give it out is also a crime. The only legal use is one the FDA allows, on a doctor’s order. The penalty is up to five years in prison, or ten years if a minor is involved.
Sport: the World Anti-Doping Agency bans growth hormone at all times.
Approval: each brand holds a biologics licence, deemed on 2020-03-23 under section 7002(e) of the BPCI Act. Labelled Genotropin regimens, as historical label facts: pediatric GH deficiency 0.16–0.24 mg/kg/week, Prader-Willi syndrome 0.24, Turner syndrome 0.33, idiopathic short stature up to 0.47 and small for gestational age up to 0.48 mg/kg/week, each divided into 6 or 7 subcutaneous injections; adult GH deficiency starting at no more than 0.04 mg/kg/week (maximum 0.08) or about 0.2 mg/day without weight adjustment, titrated to IGF-1.
Compounding: FDA’s March 2020 notice states that transitioning biological products are not eligible for the 503A and 503B exemptions, so the compounding field is recorded as restricted.
Distribution: 21 U.S.C. 333(e), in its 1990 form, covers somatrem, somatropin and analogues, treats convictions as Controlled Substances Act felonies for forfeiture purposes, and authorises DEA investigation. The 2007 systematic review above notes that distribution as an anti-ageing agent is illegal in the US.
Sport: WADA 2026 section S2.2.3 lists growth hormone and its analogues, naming lonapegsomatropin, somapacitan and somatrogon.
