Tesamorelin is a laboratory-made peptide (a short chain of amino acids) that mimics the natural hormone GHRH — the signal from the brain telling the pituitary to release growth hormone. It is the exception in this group of peptides: it went through full clinical development and in November 2010 was approved in the USA as a medicine (Egrifta) to reduce excess abdominal fat in adults with HIV and lipodystrophy. The evidence — two large placebo-controlled phase 3 trials and a meta-analysis from 2026 — is the strongest in this family. There are two caveats, though: almost all the data come from people with HIV, and the effect disappears once treatment stops.
What tesamorelin is
Tesamorelin is a synthetic analogue of human GHRH (growth-hormone-releasing hormone), developed by the Canadian company Theratechnologies (code name TH9507). In November 2010 the US Food and Drug Administration approved it as Egrifta — the first medicine for excess abdominal fat in people with HIV and lipodystrophy, a disturbance of fat distribution that can follow antiretroviral treatment. The approval covers only this narrow group; outside it, tesamorelin remains a compound under investigation, not a medicine.
How it works
GHRH acts on a “switch” (a receptor) on cells of the pituitary — a small gland at the base of the brain — and triggers a burst of growth hormone (GH). Growth hormone also acts through IGF-1 — a compound produced in the liver. Tesamorelin stimulates the same switch — it does not supply growth hormone from outside, it triggers the body's own. In 13 healthy men (Stanley et al., 2011), two weeks of daily administration raised the overnight GH concentration and the height of its pulses, and IGF-1 rose by an average of 181 µg/l. Importantly, growth hormone was still released in waves, as in a healthy body — the waves were simply higher.
Structure and origin
Natural GHRH is broken down within minutes by the enzyme DPP-IV, which snips off the first two amino acids. Tesamorelin has the full sequence of human GHRH (44 amino acids), but a short chemical tail — a hexenoic acid residue — has been attached to its start. It makes the enzyme's cut harder, so the peptide survives longer in the blood: the review by Dominikowski and colleagues (2026) gives a half-life of 26–38 minutes. That is still short: unlike CJC-1295 with DAC, which acts for many days, tesamorelin delivers a brief, daily stimulus.
Human data — two phase 3 trials
In some people treated for HIV, visceral fat — around the organs, not under the skin — builds up, and their growth-hormone secretion tends to be reduced. The key evidence is the trial by Falutz et al. from 2007 (New England Journal of Medicine): 412 people with HIV and excess abdominal fat were randomly assigned to tesamorelin 2 mg or placebo for 26 weeks. Visceral fat measured by computed tomography fell by 15.2%, while in the placebo group it rose by 5.0%. Triglycerides fell by 50 mg/dl and IGF-1 rose by 81%. Adverse events and glucose did not differ significantly between the groups.
The second phase 3 trial (Falutz et al., 2010; 404 patients, 12 months) gave a clearly smaller effect: visceral fat fell by 10.9% versus 0.6% on placebo. Waist and trunk fat improved, but subcutaneous and limb fat did not change — this selectivity for visceral fat is tesamorelin's hallmark. We report both results separately because they differ. The meta-analysis by Badran et al. (2026), pooling five randomised trials, estimated the difference from placebo at −27.7 cm² of visceral fat, −1.2 kg of trunk fat and −1.6 cm of waist, with an increase in lean body mass of 1.4 kg; subcutaneous fat and BMI did not change significantly.
The liver and other directions
The Boston group of Stanley and Grinspoon tested the effect on fatty liver. In a 2014 trial (JAMA; 50 people with HIV, 6 months) visceral fat fell by 34 cm² and liver fat fell modestly (net effect −2.9 percentage points). In a 2019 trial (Lancet HIV; 61 people with HIV and fatty liver, 12 months) liver fat fell by 37% relative to baseline, and in 35% of those treated (versus 4% on placebo) it dropped below the 5% threshold. The effect on liver histology needs further study.
What happens after stopping
In both phase 3 trials, after 26 weeks some of the tesamorelin group were switched, still blinded, to placebo. In the 2010 trial the authors state that the initial improvement was rapidly lost in them — visceral fat came back over the following six months. Tesamorelin therefore does not “fix” the cause; it works for as long as it is given.
Safety and the limits of the evidence
Tesamorelin has a full regulatory dossier. According to the Egrifta prescribing information, it must not be used in people with disruption of the hypothalamic–pituitary axis, in active cancer, in pregnancy, or in hypersensitivity. The drug raises IGF-1, a growth factor — the consequences of keeping it elevated for a long time are unknown, so its level is monitored during treatment. Swelling, joint pain and carpal tunnel syndrome can occur — typical of growth-hormone excess.
Glucose deserves a separate comment, because growth hormone blunts the action of insulin. The data are mixed: in the phase 3 trials glucose did not differ from placebo, and in 53 people with type 2 diabetes (Clemmons et al., 2017; sponsored by the manufacturer) neither the insulin response nor HbA1c worsened over 12 weeks. On the other hand, in the JAMA trial fasting glucose rose transiently after two weeks, and per the prescribing information, at 26 weeks HbA1c of 6.5% or more was seen in 5% of those treated versus 1% on placebo. Limitations: almost all participants had HIV, the trials lasted up to a year, and most were funded by the manufacturer. We deliberately give no methods of use and no doses.
The wider context — GHRH analogues
Tesamorelin belongs to the GHRH analogues, alongside sermorelin (the GHRH 1-29 fragment, formerly the medicine Geref) and CJC-1295 in its with-DAC and without-DAC versions, the latter known as Mod GRF 1-29. All act on the same switch and differ in the quality of the evidence: tesamorelin has phase 3 trials and an approval, sermorelin has old studies and a withdrawn approval, Mod GRF 1-29 has no human studies at all. A separate family are ghrelin mimetics such as ipamorelin, acting through a different receptor.
Summary
Tesamorelin is the GHRH analogue with the strongest evidence in its class: in two phase 3 trials in more than 800 people with HIV it reduced visceral fat by 11–15% over six months and left subcutaneous fat alone, and in smaller trials it also lowered liver fat. It has been a medicine in the USA since 2010, but solely for people with HIV and lipodystrophy. The effect lasts only while it is given, IGF-1 rises and needs monitoring, and data beyond HIV or beyond one year barely exist. State of the evidence: strong in a narrow indication, weak outside it.
Sources
- Badran AS, Helal A, Shata KS, Ayesh H. Body composition, hepatic fat, metabolic, and safety outcomes of Tesamorelin, a GHRH analogue, in HIV-associated lipodystrophy: A meta-analysis of randomized controlled trials. Obesity Research and Clinical Practice. 2026;20(1):2–12. PMID: 41545261. DOI: 10.1016/j.orcp.2026.01.002. pubmed.ncbi.nlm.nih.gov/41545261
- Falutz J, Allas S, Blot K, et al. Metabolic effects of a growth hormone-releasing factor in patients with HIV. New England Journal of Medicine. 2007;357(23):2359–70. PMID: 18057338. DOI: 10.1056/NEJMoa072375. pubmed.ncbi.nlm.nih.gov/18057338
- Falutz J, Potvin D, Mamputu JC, et al. Effects of tesamorelin, a growth hormone-releasing factor, in HIV-infected patients with abdominal fat accumulation: a randomized placebo-controlled trial with a safety extension. Journal of Acquired Immune Deficiency Syndromes. 2010;53(3):311–22. PMID: 20101189. DOI: 10.1097/QAI.0b013e3181cbdaff. pubmed.ncbi.nlm.nih.gov/20101189
- Stanley TL, Feldpausch MN, Oh J, et al. Effect of tesamorelin on visceral fat and liver fat in HIV-infected patients with abdominal fat accumulation: a randomized clinical trial. JAMA. 2014;312(4):380–9. PMID: 25038357. DOI: 10.1001/jama.2014.8334. pubmed.ncbi.nlm.nih.gov/25038357
- Stanley TL, Fourman LT, Feldpausch MN, et al. Effects of tesamorelin on non-alcoholic fatty liver disease in HIV: a randomised, double-blind, multicentre trial. The Lancet HIV. 2019;6(12):e821–e830. PMID: 31611038. DOI: 10.1016/S2352-3018(19)30338-8. pubmed.ncbi.nlm.nih.gov/31611038
- Stanley TL, Chen CY, Branch KL, et al. Effects of a growth hormone-releasing hormone analog on endogenous GH pulsatility and insulin sensitivity in healthy men. Journal of Clinical Endocrinology and Metabolism. 2011;96(1):150–8. PMID: 20943777. DOI: 10.1210/jc.2010-1587. pubmed.ncbi.nlm.nih.gov/20943777
- Clemmons DR, Miller S, Mamputu JC. Safety and metabolic effects of tesamorelin, a growth hormone-releasing factor analogue, in patients with type 2 diabetes: A randomized, placebo-controlled trial. PLoS One. 2017;12(6):e0179538. PMID: 28617838. DOI: 10.1371/journal.pone.0179538. pubmed.ncbi.nlm.nih.gov/28617838
- Dominikowski A, Rękoś Z, Olejarz M, et al. The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration. Frontiers in Endocrinology. 2026;17:1822475. PMID: 42395176. DOI: 10.3389/fendo.2026.1822475. pubmed.ncbi.nlm.nih.gov/42395176
For in-vitro laboratory research only. It is not a human medicine and is not for treatment.