Tesamorelin is a GHRH analogue studied for visceral fat — here is what the trials measured.

The short version

Tesamorelin is a lab-made copy of GHRH (the brain's own "make growth hormone" signal), tweaked so the body breaks it down more slowly. It nudges the pituitary gland to release more of your own growth hormone, which in turn raises IGF-1 (a growth signal the liver makes when growth hormone rises) and shrinks visceral fat (the deep belly fat packed around the organs). It is FDA-approved for one job only — reducing that deep belly fat in people with HIV-associated fat redistribution — and every other use is off-label. This page is a plain-English map of what the studies found, with each finding cited to its source.

What is tesamorelin?

Tesamorelin is a synthetic 44-amino-acid peptide — a stabilized analogue of human growth hormone-releasing hormone, GHRH(1-44) ^[6]. Its defining trick is a trans-3-hexenoic acid group bolted onto the N-terminus (the front end of the peptide chain). That modification blocks DPP-IV (an enzyme that normally chews up natural GHRH within minutes), so tesamorelin survives in the bloodstream long enough to do its work ^[6].

It is not growth hormone, and it is not a steroid. Instead of supplying a hormone from outside, it tells the pituitary gland to release more of the body's own growth hormone in its natural pulsing rhythm ^[4]. That growth hormone then drives the liver to make IGF-1, and the GH/IGF-1 pair promotes the breakdown of stored fat — preferentially in the visceral compartment ^[1]. A clinical review frames tesamorelin precisely this way: a full-length, DPP-IV-resistant GHRH analogue developed to reduce visceral fat in HIV-associated lipodystrophy ^[6]. For the full step-by-step, see how tesamorelin works.

Tesamorelin as a peptide: structure and class

As a tesamorelin peptide, the molecule sits in a well-defined class: a growth hormone-releasing hormone receptor agonist (a GHRH analogue), CAS 218949-48-5, molecular weight 5135.9 Da, ATC code H01AC06 ^[6]. Its free-base empirical formula is C221H366N72O67S, and it is supplied clinically as the acetate salt ^[6].

This class matters because it sets tesamorelin apart from two things people often confuse it with. It is not recombinant growth hormone — it works one step upstream, amplifying the body's own pulsatile secretion rather than flooding the system with continuous hormone ^[4][7]. And it is structurally distinct from sermorelin, the truncated GHRH(1-29) analogue: tesamorelin keeps the full 44-residue sequence plus the stabilizing N-terminal group ^[6]. We unpack that contrast on the tesamorelin vs sermorelin page.

What the trials reported: visceral fat, liver fat and IGF-1

The headline finding is reproducible. In the pivotal 26-week Phase 3 randomized controlled trial of 412 HIV patients with abdominal fat accumulation, tesamorelin 2 mg/day reduced visceral adipose tissue by 15.2% while placebo increased it by 5.0%; triglycerides fell by 50 mg/dL and IGF-1 rose by 81.0% ^[1]. A 2026 meta-analysis of five RCTs confirmed the pattern at scale: a pooled visceral-fat reduction of -27.71 cm2 (95% CI -38.37 to -17.06), trunk fat down 1.18 kg, hepatic fat fraction down 4.28%, and lean body mass up 1.42 kg — all P<0.001, without serious adverse events ^[15].

The liver signal is real but specific. In a 6-month JAMA RCT of 50 antiretroviral-treated HIV adults, tesamorelin produced a visceral-fat treatment effect of -42 cm2 (P=0.005) and cut hepatic lipid-to-water percentage by a net -2.9% (P=0.003) ^[3]. These are documented research findings in a defined population, not general weight-loss claims. The effect concentrated on internal abdominal fat, not on subcutaneous fat or overall BMI ^[4]. We walk each study in date order under the pivotal HIV trials.

Regulatory status: FDA-approved for HIV-associated lipodystrophy only

Tesamorelin is FDA-approved — but the scope is narrow and worth stating exactly. It was approved in the United States in 2010 (NDA 022505) to reduce excess abdominal fat in HIV-infected patients with antiretroviral-related lipodystrophy ^[5]. That is the entire approved indication. Every other use — general visceral-fat reduction, anti-aging, cosmetic fat loss, performance, non-HIV fatty-liver disease — is off-label and investigational.

These pages summarize that published record and give no human dosing instructions. The doses you will see are study doses ("studied at 2 mg/day in HIV patients"), never a recommendation. Tesamorelin is also prohibited in sport under the WADA Prohibited List, category S2 (peptide hormones, growth factors, and mimetics), both in- and out-of-competition. For the questions readers ask most, see common questions about tesamorelin.

Tesamorelin is a peptide, not a steroid

A common search is whether tesamorelin is a steroid. It is not. Steroids are small lipid-based molecules; tesamorelin is a 44-amino-acid peptide hormone analogue ^[6]. It carries no anabolic-steroid pharmacology and does not bind steroid receptors. Its only action is at the GHRH receptor on pituitary somatotrophs (the pituitary cells that make growth hormone), where it raises cAMP and triggers pulsatile growth-hormone release ^[4]. The downstream effects — higher IGF-1, visceral-fat lipolysis — flow from the body's own growth hormone, not from any steroid pathway.

Tesamorelin side effects and contraindications in the literature

Across the trial program, the most common events were injection-site reactions and growth-hormone-class effects — arthralgia (joint aches), headache, and peripheral oedema (fluid swelling); serious adverse events occurred in fewer than 4% of patients over 26 weeks ^[9]. A systematic review of 10 placebo-controlled trials (1,511 patients) found arthralgias and oedema as the statistically significant adverse effects, with the class generally well tolerated ^[10].

The FDA label lists firm contraindications: any preexisting active malignancy (treatment must be complete and the cancer inactive first), known hypersensitivity to tesamorelin or its excipients, and pregnancy — animal organogenesis studies showed hydrocephaly in offspring ^[14]. Because the drug works by raising endogenous growth hormone and IGF-1, the label carries explicit growth-factor warnings ^[14]. The NIH LiverTox monograph rates tesamorelin a likelihood score of E — an unlikely cause of clinically apparent liver injury, with no attributable cases reported ^[5]. The full side effects and contraindications are detailed in the FAQ.

How the safety data read

The safety record is unusually mature for this compound class, because tesamorelin is an approved drug with multiple controlled trials behind it. Over the 52-week program, changes in glucose parameters were not clinically significant, and visceral-fat benefit was sustained at roughly -18% ^[2]. A dedicated mechanistic study in healthy men found neither fasting glucose (P=0.93) nor insulin-stimulated glucose uptake (P=0.61) was significantly affected ^[4]. Two honest limits remain on the board, though: growth-hormone-axis stimulation raises IGF-1, a growth factor for which long-term oncologic data are limited, and visceral fat reaccumulates within weeks of discontinuation, so any benefit is contingent on continued dosing ^[2]. Every figure above is sourced in the full reference list.