Tesamorelin

Origin and structure

Tesamorelin was developed by Theratechnologies, a company in Montreal, under the code name TH9507. It is built on the complete 44-amino-acid sequence of human GHRH, the hormone from the hypothalamus that drives growth-hormone release, with one addition: a hexenoyl group, a six-carbon chain with a double bond at position 3, attached to the tyrosine at the start of the chain. The result is a stabilised analogue that, in laboratory tests, binds and activates the human GHRH receptor about as strongly as the natural hormone.

The medicine contains it as an acetate salt; the peptide itself has the formula C221H366N72O67S and a molecular weight of 5,135.9 daltons. It is short-lived in the body: on the current US labels its half-life after an injection under the skin is 8 to 11 minutes, and less than 4% of a subcutaneous dose of the original formulation reached the bloodstream.

Three versions have been sold in the US under the Egrifta name. The original came in 1 mg vials. Egrifta SV is a single-vial formulation that is mixed and injected straight away, and Egrifta WR, approved in March 2025, is mixed once a week. The labels state that each gives blood levels similar to the original, so the different milligram doses on the packs are not stronger or weaker treatments. The label doses are listed in the Dosage tab.

How it works

Tesamorelin activates the GHRH receptor on the growth-hormone-producing cells of the pituitary. The pituitary then releases more of its own growth hormone (GH) in pulses, and the liver and other tissues respond by making more IGF-1. It is therefore not growth hormone itself, and it needs a working pituitary: the label excludes people whose hypothalamic-pituitary axis has been disrupted, for example by pituitary surgery, a pituitary tumour, head irradiation or head trauma. In the trials, other pituitary hormones (TSH, LH, ACTH and prolactin) did not change in a clinically significant way.

Growth hormone breaks down stored fat, and visceral fat, the fat packed around the organs inside the abdomen, responded most in the trials. Fat under the skin of the belly barely changed, while lean body mass rose slightly. Why visceral fat is so sensitive is not fully explained; abdominal obesity goes together with reduced GH secretion, which tesamorelin raises.

Is tesamorelin approved?

In the United States, yes, for one narrow indication. In the EU, no.

The Spanish company Ferrer Internacional applied to the EMA for Egrifta to treat excess abdominal fat in HIV patients with lipodystrophy, on the basis of the two main trials with 816 patients. It withdrew the application on 21 June 2012, when the CHMP, the EMA's committee for human medicines, held the provisional opinion that Egrifta could not be approved. The committee's objections: in practice, fat from lipodystrophy is hard to distinguish from fat due to ordinary obesity, and the evidence for the proposed cut-off of more than 130 cm² of visceral fat was insufficient; the fat reduction had not been shown to bring real health benefits; the trial participants had a higher BMI and more abdominal fat than typical European HIV patients; and the rise in IGF-1, which may be linked to cancer risk and worsening diabetic eye disease, was a major safety concern, while no long-term safety data were provided for a medicine meant to be used long term.

There is no EU marketing authorisation, and tesamorelin is not a registered medicine in the Netherlands. Research-grade tesamorelin, the lyophilised peptide sold for laboratory use, is not Egrifta: it has no marketing authorisation, is not made under a medicines licence and may not be used in people.

• US: approved by the FDA in 2010 as Egrifta to reduce excess abdominal fat in HIV-infected adults with lipodystrophy. The current labels, Egrifta SV and Egrifta WR (March 2025), keep that single indication and state that it is not for weight loss, because its effect on body weight is neutral, and that its long-term cardiovascular safety has not been established.
• Sport: the 2026 WADA Prohibited List names tesamorelin in class S2.2.4, growth-hormone-releasing factors, which is prohibited in and out of competition. The same list is the appendix to the Council of Europe Anti-Doping Convention and applies in the Netherlands.

What the research shows

Almost all controlled data come from people with HIV. The approval rests on two phase 3 trials sponsored by Theratechnologies; later, smaller trials, several of them from Massachusetts General Hospital in Boston, tested liver fat and obesity without HIV, and a few looked at memory and thinking. We found no published trial that tested tesamorelin for muscle building or athletic performance in healthy people.

• First phase 3 trial (Falutz et al., NEJM 2007): 412 people with HIV and abdominal fat accumulation, randomised to tesamorelin or placebo for 26 weeks. Visceral fat fell 15.2% on tesamorelin and rose 5.0% on placebo; triglycerides fell by 50 mg/dL against a rise of 9 mg/dL, and IGF-1 rose 81%. Glucose measures did not differ, but more people on tesamorelin withdrew because of side effects.
• Both phase 3 trials pooled (Falutz et al., JCEM 2010): 806 participants randomised 2:1. At 26 weeks the treatment effect on visceral fat was −15.4%, with no significant change in fat under the skin, and triglycerides and body-image scores improved. Those who continued to week 52 kept a 17.5% reduction from baseline; on the label's figures, those switched to placebo regained visceral fat (+22% and +16% in the two trials over the next 26 weeks).
• Fatty liver in HIV (Stanley et al., Lancet HIV 2019): 61 people with HIV and at least 5% liver fat, 12 months, funded by the US National Institutes of Health. Liver fat fell 4.1 percentage points more than on placebo (95% CI −7.6 to −0.7), a 37% relative reduction, and 35% versus 4% ended below the 5% threshold. Fasting glucose and HbA1c did not differ.
• Abdominal obesity without HIV (Makimura et al., JCEM 2012): 60 adults with abdominal obesity and reduced GH secretion, 12 months. Visceral fat fell 35 cm² more than on placebo, triglycerides and CRP fell, and the carotid artery wall became slightly thinner; glucose and HbA1c did not change.
• Type 2 diabetes (Clemmons et al., PLoS One 2017): 53 patients, 12 weeks, two doses against placebo. Insulin response, fasting glucose and HbA1c did not differ between groups.
• Cognition: in 152 adults aged 55 to 87, with and without mild cognitive impairment (Baker et al., Arch Neurol 2012), 20 weeks of tesamorelin gave a favourable effect on a combined cognitive score (P = 0.03), mainly executive function, and adverse events in 68% versus 36% on placebo. A 2025 open-label trial in 73 people with HIV and abdominal obesity (Ellis et al.) found no significant difference in cognition against standard care.

Side effects and warnings

The label's safety data come from 740 people with HIV treated in the trials, 543 of them during the 26-week placebo-controlled phases. Injection-site reactions (redness, itching, pain, irritation, bruising) occurred in 25% against 14% on placebo. Next came effects linked to growth hormone and fluid retention: joint pain in 13% (11% on placebo), pain in the arms or legs, muscle pain and swollen legs in 6% each (2 to 5% on placebo), tingling in 5%, and occasionally carpal tunnel syndrome. Hypersensitivity reactions such as itching, flushing, hives and rash occurred in 4%.

Blood sugar and IGF-1 are the two things the label asks doctors to monitor. HbA1c rose to 6.5% or higher in 5% of people on tesamorelin against 1% on placebo. After 26 weeks, 47% had an IGF-1 level more than two standard deviations above normal and 36% more than three; the effects of long-lasting raised IGF-1 are unknown. Half of the treated patients developed antibodies against tesamorelin, without a loss of effect.

The label rules out use in pregnancy (in rats it caused hydrocephalus in the offspring), in active cancer and in a disrupted hypothalamic-pituitary axis, asks for careful weighing in people with a history of cancer, and notes that growth hormone has increased mortality in acute critical illness. Two long-term safety studies by the manufacturer, a planned 10-year cohort and a trial on diabetic eye disease, were terminated without posted results, and the label still states that long-term cardiovascular safety has not been established.

Tesamorelin, sermorelin and CJC-1295

All three act on the GHRH receptor, but they are different molecules with very different evidence. Tesamorelin is the full 44-amino-acid hormone with a stabilising group, and the only one of the three with a current approval, in the US. Sermorelin is a shortened copy made of the first 29 amino acids of GHRH, without a stabilising group; it was once approved in the US as Geref, but its maker stopped selling it. CJC-1295 is a modified 29-amino-acid version that was also tested in HIV-associated abdominal fat, but its phase 2 trial was stopped and it has never been approved.

No trial has compared them head to head, so online claims that one is stronger, longer-lasting or 'cleaner' than another are not based on comparative data. Each has its own article.

Frequently asked questions

Is tesamorelin legal in the Netherlands?

It is not a registered medicine in the Netherlands or anywhere in the EU, so it may not be sold, advertised or supplied for use in people; Egrifta is approved only in the US. Buying and selling it as research material is a different status, which our guide on research-use-only products in the Netherlands explains. For athletes it is a doping substance at all times.

Is tesamorelin banned in sport?

Yes, in and out of competition. The WADA Prohibited List names tesamorelin under S2.2.4, growth-hormone-releasing factors, and the Dutch anti-doping rules apply the same list. Being an approved medicine in the US does not change that; athletes with a medical need would require a therapeutic use exemption. See our guide on peptides and the doping list.

Does tesamorelin cause weight loss?

Not in the trials. Visceral fat fell, but body weight stayed the same, and lean body mass rose by 1.2 to 1.3 kg against a small fall on placebo. The US label says plainly that it is not indicated for weight loss because its effect on weight is neutral. What changes is where the fat sits, not how much a person weighs.

Why is tesamorelin not approved in Europe?

The application was withdrawn in 2012 when the EMA's CHMP was heading for a negative opinion. It found that the fat reduction had not been shown to improve health, that the trial patients were heavier than European HIV patients, that lipodystrophy fat is hard to tell from ordinary obesity, and that the rise in IGF-1 was a major safety concern without long-term data.

What happens after tesamorelin is stopped?

The visceral fat comes back. In the extension phases of both phase 3 trials, people switched from tesamorelin to placebo regained 22% and 16% of visceral fat over 26 weeks and lost 1.7 to 1.8 kg of lean mass, while those who continued kept their reduction. IGF-1 also fell back towards its starting level.

Is research-grade tesamorelin the same as Egrifta?

No. Egrifta is a licensed US medicine with a defined formulation and dose, made and tested under pharmaceutical rules; even its own versions are not interchangeable without a dose change. Research-grade tesamorelin is a lyophilised peptide sold for laboratory use; its identity and purity are what a certificate of analysis says, nothing more, and it may not be used in people. Our lab results show what we test for.

Storage and handling

Store according to product-label instructions and batch handling notes. Lyophilized research peptides are commonly kept dry, protected from light, and handled with clean laboratory technique.

References

Checked against these sources on 28 October 2026.

Related peptides