Sermorelin vs HGH: mechanism, evidence, and legal status

The short answer: sermorelin is a signal that tells the pituitary gland to release more of the body's own growth hormone, while HGH (somatropin) is growth hormone itself, injected directly. [1] [2] Somatropin is FDA approved for specific conditions such as diagnosed growth hormone deficiency; sermorelin has no approved product today, and anti-aging use of either one is off-label.

This post compares the two on mechanism, human evidence, approval, and legality. It does not give dosing advice.

How do sermorelin and HGH work?

Sermorelin is the first 29 amino acids of growth hormone releasing hormone, the hypothalamic signal that drives growth hormone release. [1] It only works if the pituitary can respond, and the body's normal feedback, which damps growth hormone when IGF-1 rises, stays in play.

Somatropin is recombinant human growth hormone: a 191 amino acid protein with the same sequence as the hormone the pituitary makes. [2] It bypasses the pituitary entirely, so it works even when the pituitary is damaged, and its effect is set by the dose rather than by the body's feedback.

What does the human evidence show?

Sermorelin. Its approval rested on pediatric trials in which growth velocity improved in children with idiopathic growth hormone deficiency. [1] In adults the data are small. In 10 healthy older men, two weeks of twice daily injections brought growth hormone and IGF-1 back up to the levels of young men, but only at the higher of two doses tested. [3] A longer adult trial, using a close sermorelin analog, gave nightly injections to 19 people aged 55 to 71 for 16 weeks: IGF-1 and skin thickness rose in both sexes, while lean body mass and insulin sensitivity improved in men only, and the only adverse effect noted was a temporary rise in blood fats. [4] No trial has tested sermorelin for fat loss, performance, or longevity.

HGH. Somatropin has decades of trial data in the conditions on its label, including growth failure in children from growth hormone deficiency, Turner syndrome, Prader-Willi syndrome, and several other causes, and growth hormone deficiency in adults. [2] In healthy older people, the picture changes. A randomized trial in 131 adults aged 65 to 88 found that growth hormone raised lean mass and cut fat, but strength did not increase significantly on growth hormone alone, and swelling, joint pain, carpal tunnel symptoms, and diabetes or glucose intolerance were common. [5]

In short, somatropin has far more evidence, almost all of it in people with a diagnosed deficiency or growth disorder. Neither drug has good evidence in healthy adults.

Which one is FDA approved?

Only somatropin, and only for its labeled indications. [2] Somatropin products were deemed biologics on March 23, 2020. [9]

Sermorelin was approved as Geref: as a diagnostic in 1990 and for treating idiopathic growth hormone deficiency in children in 1997. The sponsor stopped selling it, and FDA withdrew both approvals in 2009. In 2013 FDA published a determination that Geref was not withdrawn for reasons of safety or effectiveness. [7] There is no FDA approved sermorelin product on the market today; the sermorelin regulatory tracker logs the history.

Is either one legal to get?

Somatropin is available only by prescription, as a brand or approved product. Biological products are not eligible for the 503A or 503B compounding exemptions, so there is no lawful compounded HGH. [10] HGH is also unusual in federal law: knowingly distributing it for any use other than treating a disease or other recognized condition that FDA has authorized, on a physician's order, is a crime punishable by up to 5 years in prison. [11]

Sermorelin is widely prescribed through telehealth clinics as a compounded drug. It is not on FDA's 503A bulks list and was not placed in Category 2. [8] Many 503A pharmacies compound it on the basis of the former Geref approval, and whether that satisfies federal compounding rules depends on how a state board and the pharmacy read it. [7] Compounded products are not FDA reviewed for identity or purity. The sermorelin cost page lists dated prices from licensed programs.

Both are banned in sport: the WADA Prohibited List covers growth hormone and growth hormone releasing hormone analogues, including sermorelin, under section S2. [12]

Why is anti-aging use of either off-label?

No FDA label for either drug includes aging, and no trial has shown either one extends life or health span. The longevity page grades what has been tested.

For somatropin, the evidence runs against it. A systematic review of 18 study populations of healthy older adults found small changes in body composition (about 2.1 kg more lean mass and 2.1 kg less fat, with no change in weight) and higher rates of swelling, joint pain, carpal tunnel syndrome, and breast tissue growth, with a trend toward diabetes. The authors concluded that growth hormone cannot be recommended as an anti-aging therapy and noted that its distribution for that purpose is illegal in the United States. [6] [11]

For sermorelin, the case rests on the idea that stimulating the pituitary is gentler than replacing the hormone, because feedback limits how high growth hormone can go. That idea is plausible, but the adult trials are too small and short to show benefit or long term safety. [4]

What else is sermorelin compared with?

See sermorelin vs tesamorelin, sermorelin vs ipamorelin, sermorelin vs MK-677, and the sermorelin and ipamorelin blend page. For the approved GHRH analog, read tesamorelin vs HGH.

Talk to a clinician first

If you think you have low growth hormone, ask a licensed clinician about formal testing before starting either drug; the growth hormone deficiency page explains how it is diagnosed and what is approved to treat it.