HGH (Somatropin)

Recombinant 191-amino-acid human growth hormone, sequence-identical to the main 22 kDa pituitary isoform and FDA-approved for growth hormone deficiency and related conditions since the 1980s — and, unlike the secretagogues it is routinely confused with, governed by a federal distribution felony statute of its own.

Also referenced as: Somatropin, Human Growth Hormone, Recombinant Human Growth Hormone, rhGH, Humatrope, Genotropin, Norditropin, Omnitrope, Nutropin, Saizen, Serostim, Zorbtive

Also appears in: Performance · Longevity

What is HGH (Somatropin)?

Somatropin is recombinant human growth hormone: a 191-amino-acid, roughly 22 kDa single-chain protein produced in bacterial or mammalian expression systems. Its sequence is identical to the pituitary’s main 22 kDa growth hormone isoform — not to everything the pituitary secretes, which is a mixture of that dominant form, a 20 kDa splice variant, and other minor isoforms. That distinction is not a technicality; it is what makes recombinant hormone detectable in sport, and it is covered below.

It has been a prescription drug in the United States since the start of the recombinant era. The methionyl variant somatrem (Protropin) was approved in October 1985 and sequence-identical somatropin (Humatrope) in 1987, replacing cadaver-derived pituitary hormone — the U.S. National Hormone and Pituitary Program halted distribution in 1985 after recipients were diagnosed with Creutzfeldt-Jakob disease traced to prion contamination of pooled pituitary harvests.

Where it sits in this site’s market is worth stating plainly, because it is commonly described wrong. Somatropin is not a normal research-peptide catalog item: no vendor on our pricing board lists it, and the felony statute described under Key considerations is the straightforward reason why. What curated vendors actually stock under adjacent names are the growth hormone secretagogues (sermorelin, ipamorelin, CJC-1295, GHRP-6) and the unrelated HGH Fragment 176-191. Finished somatropin circulates instead through underground and gray-import channels as IU-labeled generic vials, outside both the pharmacy system and the vendor catalogs this site tracks.

How it works

• Somatropin binds the growth hormone receptor, which exists as a constitutive (pre-formed) dimer rather than being dimerized by the ligand; binding realigns the receptor pair and activates JAK2 tyrosine-kinase signaling and downstream STAT5 transcription (Brooks & Waters, Nature Reviews Endocrinology, 2010;6:515-525).
• Much of its growth-promoting and anabolic activity is indirect, driven by induction of insulin-like growth factor 1 (IGF-1) in the liver and peripheral tissues (Brooks & Waters, Nature Reviews Endocrinology, 2010;6:515-525).
• In growth-hormone-deficient adults, six months of replacement increased lean body mass and reduced fat mass in a double-blind, placebo-controlled trial of 24 patients, consistent with combined anabolic and lipolytic actions (Salomon et al., New England Journal of Medicine, 1989;321:1797-1803).
• It also antagonizes insulin action, and the trade-off is visible in the best-known healthy-aging study: lean mass rose and adipose mass fell, but systolic blood pressure and fasting glucose both increased significantly (Rudman et al., New England Journal of Medicine, 1990;323:1-6).

Research status

Somatropin is one of the most extensively studied protein therapeutics in existence. FDA-approved indications accumulated over four decades span pediatric and adult growth hormone deficiency, Turner syndrome, Prader-Willi syndrome, chronic kidney disease, children born small for gestational age, idiopathic short stature, SHOX deficiency, Noonan syndrome, HIV-associated wasting, and short bowel syndrome. Once-weekly long-acting versions have since been approved: somapacitan (2020), lonapegsomatropin (2021), and somatrogon (2023).

Outside true deficiency states, the controlled evidence is far less favorable:

• Rudman et al. (New England Journal of Medicine, 1990;323:1-6) — the six-month study that seeded the anti-aging market — enrolled 21 healthy men aged 61 to 81, of whom 12 received growth hormone and 9 served as untreated controls. It showed body-composition changes but also significant increases in systolic blood pressure and fasting glucose. It is worth knowing how small the treated arm actually was before treating this paper as a foundation.
• A systematic review of growth hormone in the healthy elderly (Liu et al., Annals of Internal Medicine, 2007;146:104-115) found only small body-composition changes — roughly 2.1 kg of fat lost and 2.1 kg of lean mass gained, with no change in overall weight — alongside high rates of soft-tissue edema, arthralgia, carpal tunnel syndrome, and impaired fasting glucose, and concluded it cannot be recommended as an anti-aging therapy.
• A companion review of athletic performance (Liu et al., Annals of Internal Medicine, 2008;148:747-758) found growth hormone may increase lean body mass but does not demonstrably improve strength, may worsen exercise capacity, and increases adverse events.
• Long-term safety remains under active surveillance. The French arm of the SAGhE program reported an increased all-cause mortality signal in adults treated with growth hormone as children (Carel et al., Journal of Clinical Endocrinology & Metabolism, 2012;97:416-425). The full eight-country SAGhE cohort of 24,232 patients (Sävendahl et al., The Lancet Diabetes & Endocrinology, 2020;8:683-692) then found no significant all-cause mortality increase in the lowest-risk group — isolated growth hormone deficiency and idiopathic short stature (SMR 1.1, 95% CI 0.9-1.3) — but a significant increase among patients treated for being born small for gestational age (SMR 1.5, 95% CI 1.1-1.9), sharply higher mortality in the moderate- and high-risk diagnostic groups, and elevated circulatory- and haematological-disease mortality across all risk groups.

Common dosage forms

• Pharmacy-channel somatropin is dispensed in milligram-dosed prefilled multidose pens and cartridges for daily subcutaneous injection, plus single-dose vials; long-acting weekly products come in their own prefilled pen formats.
• Gray-import generics are sold as lyophilized powder in vials labeled in international units, commonly as multi-vial kits, intended for reconstitution before injection. By the WHO standard, 1 mg of somatropin is approximately 3 IU. The IU labeling is itself a channel tell rather than a neutral convention: approved products moved to milligram dosing decades ago, so an IU-labeled vial is by definition not coming from the approved supply chain.
• Somatropin is a 22 kDa protein and is not orally bioavailable, so capsules, sprays, or topical products marketed as “HGH” cannot deliver the hormone itself.

Key considerations

• Unusually strict U.S. legal status. Section 303(e) of the Food, Drug, and Cosmetic Act (21 U.S.C. § 333(e)) makes it a felony to knowingly distribute, or possess with intent to distribute, human growth hormone for any use in humans other than a use authorized by the Secretary of HHS and ordered by a physician — punishable by up to five years, or ten where a minor is involved. This is a stricter regime than ordinary off-label rules, and it is the reason curated vendors do not carry the finished hormone. A “research use only” label does not create an exemption, because the statute turns on distribution for human use, not on the wording of the label (Perls et al., JAMA, 2005;294:2086-2090).
• Prohibited at all times in sport under the World Anti-Doping Agency Prohibited List (class S2, peptide hormones and growth factors). Detection leans on the isoform point from the opening section: recombinant somatropin is pure 22 kDa, so administration raises the 22 kDa fraction while suppressing the non-22 kDa isoforms, and that skewed ratio is what the isoform test reads.
• Naming confusion runs in two directions, and both appear in vendor listings. Somatropin is the hormone itself; sermorelin, ipamorelin, CJC-1295, and GHRP-6 are secretagogues that prompt endogenous release. Separately, HGH Fragment 176-191 — frequently listed as “HGH Frag” — is a short C-terminal fragment studied for lipolysis, not growth hormone, and shares none of its receptor activity. A listing using “HGH” as shorthand is more likely to be one of these than the hormone.
• IU-labeled gray-market vials carry no verified potency, identity, or sterility. The failure mode is documented rather than hypothetical: in 2001 the FDA and Serono warned pharmacists about counterfeit Serostim found in seven states, and the counterfeit vials contained human chorionic gonadotropin, not growth hormone at all. When an unverified vial is wrong, it is often wrong by containing a different drug entirely.
• The safety signals in controlled studies are consistent and dose-dependent — fluid retention, arthralgia, carpal tunnel syndrome, and reduced insulin sensitivity (Rudman et al., 1990; Liu et al., 2007). FDA labeling contraindicates use in active malignancy and in acute critical illness following open-heart or abdominal surgery, multiple accidental trauma, or acute respiratory failure, and long-term SAGhE mortality surveillance remains ongoing.