Sermorelin vs HGH (somatropin): differences, evidence and safety

Answer first

Sermorelin and HGH (somatropin) act at different steps of one hormone chain. Sermorelin is a 29-building-block fragment that asks the pituitary gland to release growth hormone; somatropin is the hormone itself. Somatropin is an approved prescription medicine, while sermorelin's American approvals ended in 2009. No randomised trial comparing the two could be found.

At a glance

How they work

Both substances end in the same place, more growth hormone activity in the body. They get there by different routes, one step apart in the same hormone chain.

Sermorelin

• It is a chain of 29 amino acid building blocks, matching the front section of growth hormone releasing hormone. The natural hormone is 44 building blocks long; this is the shortest piece that keeps its full activity ^[1].
• It docks onto the receptor for that hormone on the growth hormone cells of the pituitary gland, and switches them on ^[1], ^[2].
• The gland then releases growth hormone in bursts, the way this system normally works ^[1].
• Somatostatin, the hormone that damps this circuit, keeps working, because the signal still passes through the gland ^[1].

HGH (somatropin)

• It is the complete human growth hormone, made in the laboratory. Its 191 amino acids follow the same sequence as the pituitary hormone ^[3], ^[4].
• It binds the growth hormone receptor on liver, cartilage, bone, muscle and fat cells, and acts on them directly ^[4].
• It raises IGF-1, a messenger made mainly in the liver, and much of the growth effect arrives that way ^[4].
• It increases the breakdown of stored fat and lowers sensitivity to insulin, which is why diabetes can become visible under treatment ^[4].

The key difference is where each one acts. Sermorelin asks the pituitary gland for more of the body's own hormone. Somatropin bypasses the gland and its brake altogether ^[1]. The drug coding system separates them too: somatropin is H01AC01 and sermorelin H01AC04 ^[5].

Sermorelin has a half-life of roughly 10 to 20 minutes, because the kidneys filter it out and enzymes clip its front end ^[6]. Somatropin has a half-life of 3.0 ± 1.44 hours after an injection under the skin, and of 0.4 hours given into a vein. Its peak level arrives after 5.9 ± 1.65 hours ^[4].

What the studies show

No randomised trial that compares sermorelin and HGH directly could be found in the published record reviewed for this page. Three older sources touch on both in children with growth hormone deficiency, one of them by treating the same children with each in turn. None of them randomised the children.

Head-to-head: growth in children

Sequential series, same children Nine children whose growth hormone deficiency followed radiotherapy to the head were treated with sermorelin for a year. Their growth speed rose from 3.3 centimetres a year to 6.0 (p = 0.004) ^[7].

In the following year, on growth hormone instead, the same children grew at 7.5 centimetres a year. The growth hormone year always came second, so this is not a randomised comparison ^[7].

Narrative review A 1999 review compared published studies indirectly. It concluded that the gain in growth speed under sermorelin was smaller than under the same amount of growth hormone. No head-to-head trial at the approved strengths could be found by the review, and the effect on adult height was not reported ^[1].

Open treatment series The earliest sermorelin series treated 18 children, 14 of whom had previously had growth hormone. Growth speed increased in 12 of the 18. Four of the 14 previously treated children grew more slowly on sermorelin, for reasons the authors could not explain ^[8].

Sermorelin: the approval study in children

Open-label multicentre study The study behind the 1997 American approval enrolled 110 previously untreated children before puberty. Of these, 86 entered the efficacy analysis. Their average growth speed rose from 4.1 centimetres a year to 8.0 after six months, and settled at 7.2 after twelve months ^[9].

At six months, 74 per cent of the children counted as good responders. There was no comparison group ^[9].

Somatropin: trials in children with growth disorders

RCT One randomised, open trial followed 177 children with idiopathic short stature to their final adult height. Across both treated arms, final height was 9.8 cm higher in girls and 5.0 cm higher in boys than in untreated controls ^[4].

A gain of one full standard deviation in height occurred in 10 per cent of untreated children. In the lower arm it was 50 per cent, in the higher one 69 per cent ^[4].

RCT Four randomised, open trials treated 209 children aged two to eight who were born small and had not caught up in growth. Over 24 months, height scores improved by 1.2 standard deviations in the lower arm and 1.7 in the higher one. Untreated children moved by 0.1 ^[4].

These trials had untreated control groups, which the sermorelin studies in children lacked. Every participant had a diagnosed growth disorder ^[4].

Older adults

Placebo-controlled study For sermorelin, ten women and nine men aged 55 to 71 had four weeks of placebo followed by 16 weeks of active treatment. Growth hormone release began within 10 minutes and lasted about two hours ^[10].

In the same group, growth hormone secretion rose by 107 per cent in the men and 70 per cent in the women (p < 0.05). IGF-1 rose by 28 per cent (p < 0.001). These are laboratory values; no clinical benefit was measured ^[11].

Open treatment series Eleven healthy men aged 64 to 76 were treated for six weeks. Two of six strength measures improved. Weight, body mass index, the scan measurements of muscle and fat, blood sugar and blood fats all stayed where they were ^[12].

Systematic review For somatropin, a review covered 220 healthy older adults, average age 69, treated for an average of 27 weeks. Fat mass fell by 2.1 kg and lean mass rose by 2.1 kg, while body weight did not change, at plus 0.1 kg ^[13].

Swelling, joint pain, carpal tunnel syndrome and breast tissue growth in men were all significantly more common. The authors concluded that growth hormone cannot be advised as an anti-ageing therapy ^[13].

Healthy adults and performance

Systematic review For somatropin, a review of 27 study samples covered 303 physically fit people aged 13 to 45. Lean body mass was 2.1 kg higher than in control groups. Strength and exercise capacity did not improve, and swelling and exhaustion were more common ^[14].

Meta-analysis An independent analysis of 11 placebo-controlled trials in 254 healthy young adults found no improvement in muscle strength (p = 0.36). Maximal oxygen uptake did not change either (p = 0.89) ^[15].

For sermorelin, no controlled study of athletic performance, falls or everyday muscle function could be found in the sources reviewed for this page ^[16].

Long-term follow-up

Observational For somatropin, the largest cohort followed 24,232 people treated as children in eight European countries for more than 400,000 person-years. In the low-risk group, overall mortality was not significantly raised, at 1.1 times the general population. Deaths from circulatory and blood disorders were raised in every risk group ^[17].

For sermorelin, no long-term safety study could be found, and the final adult height of the treated children was not reported in the sources reviewed ^[1], ^[16].

These results come from different populations, study designs, endpoints and durations. The figures for sermorelin and somatropin therefore cannot be set against each other, apart from the small sequential series above.

Safety

The two safety records differ mainly in how much is known. Somatropin has a current American label drawn from large approval trials and long extension studies. For sermorelin, no product information sheet for either former product is publicly available any more ^[18].

Sermorelin, from the published studies:

• Brief facial flushing and pain at the injection site were the most frequently reported events. The review that reports them gives no percentages ^[1].
• Antibodies against the hormone in 14 of 18 children in the 1987 series. They had no visible effect on growth or on the response to treatment ^[8].
• Slower growth in four of 14 children who had previously had growth hormone. The cause was not established ^[8].
• Bone age moving faster than height. In children treated after radiotherapy, bone age advanced by 1.1 years per calendar year ^[7].
• Formal contraindications cannot be stated, because no valid product information sheet is available. The sources reviewed contain no data on pregnancy, breastfeeding, or impaired kidney or liver function ^[18].

Somatropin, from the American label:

• Swelling in 17.5 per cent against 5.1 per cent on placebo in the first six months. The figures come from 573 treated adults and 572 on placebo ^[4].
• Joint pain in 17.3 per cent against 4.2 per cent. Tingling affected 9.6 per cent against 1.9 per cent ^[4].
• Carpal tunnel syndrome in 61 of 3,031 patients in the long-term extension studies. New diabetes appeared in 12 of 3,031 patients, all of whom already had risk factors ^[4].
• Antibodies against the hormone in 8 of 413 children, none with a reduced growth response ^[4].
• Situations that rule it out entirely include critical illness after heart or abdominal surgery, multiple trauma or acute respiratory failure. Active cancer and closed growth plates in children rule it out as well ^[4].
• Sudden deaths have been reported in children with Prader-Willi syndrome who are severely obese or have breathing problems ^[4].
• Further warnings cover raised pressure inside the skull and a slipped growth plate at the hip ^[4].

Material bought outside a pharmacy carries a separate problem for both substances. Its composition, strength and purity are unverified.

Why this page lists no doses. Somatropin is a prescription-only medicine in every market checked, and sermorelin is prescription-only by name in Germany and Australia. Choosing an amount belongs with a doctor and valid product information. This page therefore reports what the studies measured without repeating the amounts they used.

Legal status

Somatropin is approved and prescription-only in all seven markets checked; the oldest American approval dates from 16 October 1986 ^[19]. Australia also restricts possession without authority ^[20]. In the United States, supplying it for anything but an approved condition is a federal offence ^[21]. Sermorelin's American approvals from 1990 and 1997 ended on 18 June 2009 at the maker's request ^[22], ^[23]. In 2013 the regulator found it was not for reasons of safety or effectiveness ^[24]. None of the seven markets checked licenses it now; Germany and Australia list it as prescription-only ^[25], ^[26]. Both are banned in sport at all times, somatropin under S2.2.3 and sermorelin under S2.2.4 ^[27]. Status: 10 and 15 September 2026.

Used together?

The blend directory lists no product that combines sermorelin and somatropin, and neither substance appears in any of its mixtures. The full list is under blends.

No study of sermorelin and somatropin given together could be found in the sources reviewed for this page. The sources therefore contain no data on its effect or safety. Both are named on the prohibited list, as described on peptides banned in sport. More detail on each substance is under sermorelin and somatropin.

Frequently asked questions

Which is better, sermorelin or HGH (somatropin)?

No ranking is possible from the sources reviewed for this page. In nine children with growth hormone deficiency, growth speed was 6.0 centimetres a year on sermorelin and 7.5 the following year on growth hormone. A 1999 review, comparing published studies indirectly, found a smaller gain in growth speed on sermorelin than on the same amount of growth hormone. Neither was a randomised comparison.

Is sermorelin or HGH safer?

No study comparing their safety could be found, so no ranking is possible. Somatropin has an official label with measured frequencies, for example swelling in 17.5 per cent against 5.1 per cent on placebo. Sermorelin has no current product information, and its record rests on small, older studies that report flushing and injection-site pain without percentages.

What is the difference between sermorelin and HGH?

Sermorelin copies the first 29 building blocks of growth hormone releasing hormone. That is the brain signal telling the pituitary gland to release growth hormone. HGH, or somatropin, is the complete growth hormone of 191 amino acids. Sermorelin works one step earlier and depends on the gland responding, while somatropin acts on the body's tissues directly.

Can sermorelin and HGH be taken together?

No study of sermorelin and somatropin given together could be found in the sources reviewed for this page. The sources therefore contain no data on the effect or the safety of the combination. The blend directory lists no product that contains both.

HGH 191aa vs HGH: is there a difference?

No. HGH 191aa is a grey-market label for somatropin, and every product approved in the seven markets checked is a chain of exactly 191 amino acids. The number marks the contrast with somatrem, a 192-amino-acid form from the 1980s with one extra methionine at the front, which is no longer marketed. The label describes the same molecule, not a grade or a purer version, and says nothing verified about what a grey-market vial contains.

Does sermorelin contain HGH?

No. Sermorelin contains no growth hormone. It is a fragment of the releasing hormone and makes the pituitary gland release the body's own growth hormone. The body's brake, somatostatin, therefore still applies. The drug coding system lists them separately, somatropin as H01AC01 and sermorelin as H01AC04.

Are sermorelin and HGH FDA-approved?

Somatropin is, and its oldest American approval dates from 16 October 1986. Sermorelin was approved in 1990 as a diagnostic test and in 1997 for children with growth hormone deficiency. Both approvals ended on 18 June 2009 at the maker's request. In March 2013 the regulator found that neither sermorelin product was withdrawn for reasons of safety or effectiveness.

Are sermorelin and HGH banned in sport?

Yes, both at all times, in competition and out of it, and both as non-specified substances. The 2026 prohibited list names growth hormone in section S2.2.3 and sermorelin in section S2.2.4, among the growth hormone releasing factors. German anti-doping law names both as well.

How long do sermorelin and HGH stay in the body?

Sermorelin leaves the blood within minutes, with a half-life of roughly 10 to 20 minutes in human plasma. Somatropin lasts longer: after an injection under the skin its half-life is 3.0 hours, and peak levels arrive after 5.9 hours. Given into a vein, its half-life is 0.4 hours.