Tesamorelin

Tesamorelin is a synthetic copy of the full 44-amino-acid human growth hormone-releasing hormone, GHRH(1-44), with one change: a short six-carbon hexenoyl chain attached to the first amino acid (tyrosine). The US prescribing information describes it in exactly these terms and gives a molecular weight of 5,135.9 Da for the free base ^[1]. The modification is intended to make the molecule more resistant to enzymatic breakdown than native GHRH while leaving its receptor activity intact.

It was developed by the Canadian company Theratechnologies under the code TH9507, and it is a licensed treatment in the US and Canada. That makes it different from related peptides such as sermorelin, whose licence lapsed in 2009, and CJC-1295, which never completed development.

Research-peptide suppliers also sell tesamorelin in vials labelled for laboratory use. Those products are not the licensed medicine, have not been assessed by any regulator, and their content depends entirely on the supplier; see what research peptides are.

Tesamorelin binds the GHRH receptor on somatotroph cells in the anterior pituitary, the same receptor used by the body’s own GHRH. That prompts the pituitary to release growth hormone (GH) in its natural pulses, and GH in turn raises insulin-like growth factor 1 (IGF-1), mostly made in the liver. In the first phase 3 trial, IGF-1 rose by 81% on average over 26 weeks with tesamorelin, compared with a 5% fall on placebo ^[2].

Because it acts upstream of the pituitary, tesamorelin still depends on the normal feedback system (somatostatin and IGF-1 can damp its effect). This is the main theoretical difference from injecting growth hormone itself. GH is lipolytic, and visceral fat appears to be particularly responsive, which is the basis for its licensed use in HIV-associated central fat gain.

The GHRH route is separate from the ghrelin-receptor route used by ipamorelin, GHRP-2 and GHRP-6. The two pathways add together, which is why GHRH analogues and ghrelin mimetics are often discussed as a pair, though tesamorelin itself has not been studied in combination with them.

The pivotal evidence comes from two multicentre, double-blind phase 3 trials in people with HIV on antiretroviral therapy who had accumulated abdominal fat. In the first, published in the New England Journal of Medicine, 412 patients were randomised to 2 mg tesamorelin or placebo daily for 26 weeks. Visceral fat measured by CT fell by 15.2% with tesamorelin and rose by 5.0% with placebo; triglycerides and the total-to-HDL cholesterol ratio also improved, with no significant difference in glucose measures ^[2].

A pooled analysis of both phase 3 trials (806 patients) found a treatment effect on visceral fat of about -15% at 26 weeks, with no significant change in subcutaneous abdominal fat, improvements in triglycerides and in patient-rated belly appearance, and no clinically meaningful change in glucose over 52 weeks ^[3]. In the extension phase of the first trial, the fall in visceral fat was sustained at -18% over 52 weeks of treatment, but it reaccumulated when tesamorelin was stopped ^[4]. In other words, the effect lasts only as long as treatment does.

A 2026 meta-analysis of five randomised placebo-controlled trials in HIV lipodystrophy confirmed reductions in visceral fat, liver fat and waist circumference and an increase in lean body mass, with no significant change in BMI, subcutaneous fat or CD4 count; adverse events included joint and muscle pain, tingling and injection-site redness ^[5].

Because visceral fat and liver fat tend to travel together, tesamorelin has been tested in HIV-associated fatty liver. In a 50-person randomised trial at Massachusetts General Hospital, six months of 2 mg daily reduced both visceral fat and liver fat compared with placebo; fasting glucose rose slightly at two weeks but the difference had disappeared by six months ^[6].

A larger follow-up, a 12-month randomised double-blind trial of 61 people with HIV and non-alcoholic fatty liver disease published in Lancet HIV, found a 37% relative reduction in liver fat fraction versus placebo; 35% of the tesamorelin group and 4% of the placebo group ended with liver fat below the 5% threshold ^[7]. The authors described the result as promising but said longer studies of liver histology are needed. Neither liver indication is licensed.

Outside HIV, the best-known study is a 20-week randomised placebo-controlled trial in 152 adults aged 55 to 87, including 66 with mild cognitive impairment. Participants injected 1 mg tesamorelin nightly. The GHRH group showed a favourable effect on a composite cognitive score, driven mainly by executive function, alongside a 117% rise in IGF-1 and a 7.4% fall in body fat; adverse events, mostly mild, were reported by 68% on tesamorelin and 36% on placebo ^[8].

A later open-label phase 2 trial in 73 people with HIV, abdominal obesity and neurocognitive impairment found that tesamorelin reduced waist circumference but did not improve cognition more than standard care over six months ^[9]. The evidence for cognitive effects is therefore mixed, and there is no licensed cognitive use.

Tesamorelin has also been tested in people with type 2 diabetes, a group in whom raising GH could in theory worsen glucose control. In a 12-week randomised trial of 53 patients, neither 1 mg nor 2 mg daily changed insulin response, fasting glucose or HbA1c compared with placebo ^[10].

Tesamorelin has one of the strongest human evidence bases of any peptide covered on this site: two phase 3 RCTs with more than 800 participants between them ^[2][3], long-term extension data ^[4], a meta-analysis of randomised trials ^[5], and several smaller investigator-led RCTs in liver fat, diabetes and cognition ^{[6][7][8][10]}.

The limits are equally clear. Almost all of the efficacy data come from people with HIV on antiretroviral therapy, the fat reduction reverses when treatment stops, and long-term cardiovascular outcomes have not been established; the US label states this directly ^[1]. There is no good evidence on its use by healthy people for body composition, and it is not licensed for weight loss.

Both are GHRH analogues that act on the same pituitary receptor, but they are not interchangeable. Tesamorelin is the full 44-amino-acid hormone with a stabilising hexenoyl group, and it has phase 3 randomised trial evidence and a current licence for HIV-associated abdominal fat ^[1][2]. Sermorelin is the shorter, unmodified 1-29 fragment; it was licensed in the US as Geref for diagnosing and treating growth hormone deficiency in children, but the manufacturer discontinued it in 2008, and its adult evidence consists of small, short studies. No trial has compared the two head to head, so claims that one is “stronger” or “better” are not supported by direct evidence.

The phase 3 trials, the liver-fat trials and the Lancet HIV study all used 2 mg tesamorelin injected under the skin once daily ^[2][3][6][7]. The cognition trial in older adults used 1 mg once daily at bedtime ^[8], and the diabetes safety trial compared 1 mg and 2 mg daily ^[10].

The currently marketed US formulation, Egrifta WR, is more concentrated and its labelled dose is 1.28 mg once daily; the label notes that it and the older Egrifta SV formulation differ in dosage and are not substitutable ^[1]. These figures describe what trials and the licensed product use; they are not a recommendation. If you are working out concentrations for laboratory purposes, our peptide calculator shows the arithmetic.

In the licensed product’s trials, the most common adverse reactions (reported by more than 5% of patients) were joint pain, injection-site redness and itching, pain in the extremities, swelling of the lower limbs and muscle pain ^[1]. More patients on tesamorelin than placebo withdrew because of adverse events in the first phase 3 trial, although overall adverse-event rates did not differ significantly ^[2].

The US label lists warnings that follow from raising GH and IGF-1: fluid retention (including oedema, joint pain and carpal tunnel syndrome), glucose intolerance or diabetes, hypersensitivity reactions, and a theoretical increased risk of cancer growth, so it is contraindicated in active malignancy. It is also contraindicated in pregnancy and in people with disrupted pituitary function, and IGF-1 monitoring is advised ^[1].

None of this safety information applies automatically to unlicensed research-grade material, where purity, peptide content and sterility are unknown unless independently tested.

The US FDA approved tesamorelin (Egrifta) in 2010 for reducing excess abdominal fat in adults with HIV and lipodystrophy ^[1]. A more concentrated formulation, Egrifta WR, was approved in March 2025 and became available in September 2025, according to the manufacturer. Health Canada approved Egrifta in April 2014.

In Europe, the marketing application was withdrawn in 2012 after the EMA’s medicines committee indicated it could not conclude that the benefit-risk balance was positive, citing doubts that the fat reduction translated into meaningful health benefits. As far as we could confirm, tesamorelin is not a licensed medicine in the UK, Australia or New Zealand. Rules on buying peptides differ by country; see our legal status overview and the US page.

Tesamorelin is named on the World Anti-Doping Agency Prohibited List under S2 (growth hormone releasing factors) and is banned in and out of competition ^[11].

The licensed Egrifta WR vials are stored at room temperature (20–25°C), protected from light and not frozen; once mixed with the supplied bacteriostatic water, a vial is used for seven days and then discarded ^[1]. Those instructions apply to that specific formulation only.

Research-grade tesamorelin is a different product with no validated stability data. General practice for freeze-dried peptides is covered in our guide to storing peptides.

Tesamorelin is one of the more expensive research peptides because of its size. If you are comparing suppliers, compare prices on a per-milligram basis, check the certificate of analysis using our guide on how to read a COA, and favour third-party tested suppliers.