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

Answer first

Tesamorelin and HGH (somatropin) act at different steps of the same hormone chain. Tesamorelin prompts the pituitary gland to release the body's own growth hormone, while somatropin is growth hormone itself. Tesamorelin is prescribed only in the United States, for belly fat in adults with HIV. Somatropin is approved in all seven markets checked. No direct comparison could be found.

At a glance

How they work

Both substances end up raising growth hormone activity in the body, but they enter the chain at different points. The drug classification system files them in the same group, with separate codes: H01AC06 for tesamorelin and H01AC01 for somatropin ^[1].

Tesamorelin

• It is a laboratory-made copy of growth hormone releasing factor, the brain hormone that tells the pituitary gland to release growth hormone. It carries all 44 amino acid building blocks of the natural hormone ^[2].
• A small six-carbon group (a hexenoyl group) at the front end slows its breakdown ^[2].
• It binds to docking points on the pituitary gland, which then releases growth hormone in the pulses that are normal for this system ^[2].
• In patients it raises IGF-1, a messenger made mainly in the liver, and its carrier protein IGFBP-3. Other pituitary hormones did not shift meaningfully in the approval trials ^[2].

HGH (somatropin)

• It is the complete human hormone, made in the laboratory: a single chain of 191 amino acids, matching the hormone from the pituitary gland ^[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 and increases the breakdown of stored fat. It also lowers sensitivity to insulin, which is why diabetes can become visible under treatment ^[4].

The key difference is the step. Tesamorelin asks the pituitary gland for more of the body's own hormone. Injected growth hormone bypasses the pituitary gland altogether ^[2], ^[4].

The two also differ in size and in how long they last. Tesamorelin weighs 5,135.9 daltons and has a half-life of about 11 minutes in healthy adults, peaking after a median of 0.15 hours ^[2]. Somatropin weighs 22,124.8 daltons. Its half-life after injection under the skin is 3.0 ± 1.44 hours, with a peak after 5.9 ± 1.65 hours ^[3], ^[4].

What the studies show

No study that compares tesamorelin and HGH (somatropin) directly could be found in the published record reviewed for this page. Each was tested in its own populations and for its own purposes. What follows are the separate studies of each substance.

Tesamorelin: deep belly fat in people with HIV

Phase 3 RCT The first approval trial randomised 412 adults with HIV and lipodystrophy, a condition in which body fat is redistributed in an unusual way. After 26 weeks the deep fat around the organs had fallen by 15.2 per cent on treatment and risen by 5.0 per cent on placebo (p < 0.001) ^[5].

Phase 3 RCT The second trial followed 404 adults for six months. The deep fat fell by 10.9 per cent, against 0.6 per cent on placebo (p < 0.0001). Fat on the arms and legs did not change, and neither did the fat just under the skin of the belly ^[6].

Meta-analysis Pooling five randomised trials, the difference against placebo averaged 27.71 square centimetres of visceral fat. Body mass index did not change significantly ^[7].

Body weight stayed where it was. It moved by −0.4 kg in the first trial and +0.5 kg in the second, neither different from placebo. The label states that the drug is not indicated for weight loss, because its effect on weight is neutral ^[2].

RCT In 61 people with HIV and a fatty liver, twelve months of tesamorelin lowered the liver fat fraction by 4.1 percentage points more than placebo (p = 0.018) ^[8].

Somatropin: children with growth disorders

RCT The approvals rest largely on trials in children with diagnosed growth disorders. In an open trial of 177 children with idiopathic short stature, followed to adult height, the gain in final height score against untreated controls was 0.53 standard deviations in the lower arm and 0.94 in the higher arm ^[4].

RCT In two small open trials in children with Prader-Willi syndrome, fat mass fell by 0.9 kg under treatment. In untreated children it rose by 2.3 kg (p < 0.005). Body weight changed almost identically in both groups ^[4].

RCT Six randomised trials in 172 adults with growth hormone deficiency compared treatment against placebo for six months. Lean mass rose, while body fat and waist size fell. The label reports no numbers for these endpoints, and the trials did not measure fractures, heart attacks or survival ^[4].

Somatropin: healthy adults and older adults

Systematic review A review of 303 physically fit adults found lean body mass 2.1 kg higher than in control groups. Strength and exercise capacity did not improve, and swelling and exhaustion were more common ^[9].

Meta-analysis An independent analysis of 11 placebo-controlled trials in 254 healthy young adults found no gain in muscle strength (p = 0.36) and none in maximal oxygen uptake (p = 0.89) ^[10].

Systematic review In 220 healthy older adults, average age 69, fat mass fell by 2.1 kg and lean mass rose by 2.1 kg. Body weight did not change, at plus 0.1 kg. The authors concluded that growth hormone cannot be advised as an anti-ageing therapy ^[11].

Tesamorelin: thinking and memory in older adults

Phase 2 RCT An academic trial treated 152 adults, aged 55 to 87, for 20 weeks, 66 of them with mild cognitive impairment. It found a favourable overall effect on thinking tests (p = 0.03), mainly in planning and mental flexibility. Its only approval covers belly fat in HIV, not memory ^[2], ^[12].

Where the studies fell short

Phase 2 RCT A later tesamorelin trial in 73 people with HIV and abdominal obesity found no cognitive advantage over the comparison group (p = 0.673). The trial was open-label, and its authors call it underpowered ^[13].

Phase 2 RCT In 53 adults with type 2 diabetes, twelve weeks of tesamorelin changed nothing measurable in the insulin response, fasting glucose or long-term blood sugar ^[14].

For somatropin in healthy people, the two reviews above found no gain in strength, exercise capacity or maximal oxygen uptake ^[9], ^[10]. In adults with growth hormone deficiency, whether replacement changes hard outcomes remains open ^[4].

What happens after stopping

Phase 3 RCT In the tesamorelin extension phase, 263 participants were randomised again for a further 26 weeks. Those switched to placebo lost the gains, and the deep belly fat accumulated again ^[15]. No comparable stopping study for somatropin could be found in the sources reviewed for this page.

These results come from different populations, doses, endpoints and study lengths. The figures for tesamorelin and somatropin therefore cannot be set against each other.

Safety

Both substances have an official American label with measured frequencies. Several effects overlap, because both raise growth hormone activity: swelling, joint pain, tingling and carpal tunnel syndrome appear in both labels. The trial populations differ, so the percentages are not a ranking.

Tesamorelin, from the American label:

• Injection-site reactions in 17 per cent against 6 per cent on placebo over the first 26 weeks ^[2].
• Joint pain in 13 per cent against 11 per cent. Swelling of the ankles and feet affected 6 per cent against 2 per cent ^[2].
• Carpal tunnel syndrome in 1 per cent against none on placebo. A database study found it over-reported for tesamorelin, which describes a reporting pattern rather than a cause ^[2], ^[16].
• Higher blood sugar. The odds of developing diabetes were raised (odds ratio 3.3; 1.4 to 9.6) ^[2].
• Raised IGF-1 in 47 per cent at 26 weeks, more than two standard deviations above normal. Antibodies appeared in 50 per cent, without a visible change in effect ^[2].

HGH (somatropin), from the American label and long-term cohorts:

• Swelling in 17.5 per cent against 5.1 per cent on placebo in the first six months, in 573 treated adults against 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 (2.0 per cent) and new diabetes in 12 of 3,031 (0.4 per cent) in the long-term extension studies ^[4].
• Sudden deaths have been reported in children with Prader-Willi syndrome who are severely obese or have breathing problems. The label rules the medicine out in that group ^[4].
• Long-term deaths. In 24,232 people treated as children, deaths from circulatory and blood disorders were raised in every risk group ^[17]. A cancer analysis of the same cohort found bone and bladder cancer incidence raised in patients with a growth disorder alone ^[18].

Situations that rule them out. Both labels list an active cancer as a contraindication. Tesamorelin is also ruled out with a disrupted link between the hypothalamus and the pituitary gland, a known allergy, or pregnancy ^[2]. Somatropin is also ruled out in critical illness after surgery or trauma, active or severe diabetic eye disease, and closed growth plates in children ^[4].

Material bought outside a pharmacy adds a separate problem. Tesamorelin circulates as a research compound of unverified composition ^[19]. European enforcement laboratories found growth hormone in seized consignments, alongside samples with no active ingredient at all ^[20].

Why this page lists no doses. Both substances are prescription medicines, and in the United States supplying growth hormone for anything other than an approved condition is a criminal offence ^[21]. Choosing an amount is a matter for a doctor and the official product information, so this page reports what the studies measured without repeating the amounts they used.

Legal status

Tesamorelin has been approved in the United States since 10 November 2010 and only for belly fat in adults with HIV and lipodystrophy ^[22]. The European application was withdrawn on 21 June 2012, and the Canadian product was cancelled on 30 September 2022 ^[23], ^[24]. Somatropin has been approved in the United States since 16 October 1986 and is prescription-only in all seven markets checked ^[25], ^[26]. Australia also restricts possession ^[27]. Both are banned in sport at all times: somatropin under S2.2.3, tesamorelin under S2.2.4 of the 2026 list ^[28]. Status: 7 and 15 September 2026.

Used together?

The blend directory lists no product that combines tesamorelin and somatropin. Tesamorelin appears there only in mixtures with other peptides, such as Tesamorelin + Ipamorelin, and each carries the note that the mixture holds no approval. The full list is under blends.

No study of tesamorelin and somatropin given together could be found in the sources reviewed for this page. Nothing published could be found on what the combination does or how safe it is. The individual pages for tesamorelin and somatropin set out each substance in full.

Frequently asked questions

Which is better, tesamorelin or HGH (somatropin)?

Neither can be ranked, because no study comparing them could be found. In adults with HIV and lipodystrophy, tesamorelin reduced deep belly fat by 15.2 per cent over 26 weeks, while it rose by 5.0 per cent on placebo. Somatropin was tested mainly in children with growth disorders and in adults with growth hormone deficiency. The populations, endpoints and designs differ too much for a verdict.

Is tesamorelin or HGH (somatropin) safer?

No study comparing their safety directly could be found, so no ranking is possible. Both labels report swelling, joint pain and carpal tunnel syndrome, because both raise growth hormone activity. Tesamorelin raised the odds of diabetes in its trials, and somatropin can unmask diabetes as well. The trial populations differ, so the percentages cannot be set against each other.

What is the difference between tesamorelin and HGH (somatropin)?

Tesamorelin is a copy of the brain hormone that tells the pituitary gland to release growth hormone. Somatropin is growth hormone itself, a chain of 191 amino acids that bypasses the pituitary gland. Legally, tesamorelin is a prescription medicine only in the United States, for belly fat in adults with HIV. Somatropin is approved and prescription-only in all seven markets checked.

Can tesamorelin and HGH (somatropin) be taken together?

No study of the two given together could be found, so nothing is known about the effect or the safety of the combination. The blend directory lists no product that contains both. This page describes the state of research and gives no guidance on use.

Is tesamorelin a form of HGH?

No. Tesamorelin contains no growth hormone. It is a 44-building-block copy of growth hormone releasing factor and prompts the body to release its own hormone. The drug classification system lists both in the same group, but with separate codes, and the anti-doping list places them in separate sections.

Which is better for fat loss, tesamorelin or HGH (somatropin)?

No study comparing them on any fat measure could be found. Tesamorelin reduced deep belly fat in adults with HIV, yet its label states that it is not indicated for weight loss because its effect on weight is neutral. In healthy older adults, somatropin lowered fat mass by 2.1 kg while body weight stayed unchanged, and the authors concluded that growth hormone cannot be advised as an anti-ageing therapy.

Is HGH 191AA the same as somatropin?

As a name, yes. HGH 191AA is a grey-market label for somatropin, not a grade or a purity claim. The number counts the amino acid building blocks, and every product approved in the markets checked has exactly those 191. The label marks the contrast with somatrem, a separate 192-amino-acid substance that is no longer marketed. What grey-market material sold under that label actually contains is unverified.

Are tesamorelin and HGH (somatropin) banned in sport?

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

Do tesamorelin and HGH (somatropin) need a prescription?

Yes, wherever they are approved. Tesamorelin is a prescription medicine in the United States only, and the Canadian product has been cancelled. Somatropin is prescription-only in all seven markets checked. In the United States, supplying growth hormone for any use other than an approved condition is a federal offence carrying up to five years in prison.