Tesamorelin stimulates the body's own growth hormone and selectively reduces visceral fat in the research literature.

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. Instead of injecting growth hormone directly, it nudges the pituitary gland to release more of its own. That extra growth hormone raises IGF-1 (a growth signal the liver makes when growth hormone rises) and burns off visceral fat (the deep belly fat packed around the organs). In trials it was studied at 2 mg a day in HIV patients, where it cut visceral fat by about 15-18%. It is FDA-approved only for that HIV use; every other use is off-label.

What Is Tesamorelin?

Tesamorelin is a synthetic 44-amino-acid analogue of human growth hormone-releasing hormone, GHRH(1-44), carrying a trans-3-hexenoyl group on its N-terminus that blocks the enzyme DPP-IV (dipeptidyl peptidase-IV, a protease that rapidly chews up native GHRH) ^[4]. That single modification is the whole point: native GHRH is destroyed within minutes, while the modified molecule survives long enough to do its job ^[6]. Its molecular weight is 5135.9 Da and its CAS number is 218949-48-5.

It is not a growth hormone and it is not exogenous hormone replacement. It is a secretagogue — a compound that prompts a gland to release its own hormone. Tesamorelin was approved by the FDA in 2010 (NDA 022505) for one indication only: reducing excess abdominal visceral fat in adults with HIV-associated lipodystrophy ^[5]. The pivotal evidence is unusually deep for a peptide of this class — two Phase 3 randomized controlled trials in over 800 HIV patients combined, plus a JAMA hepatic-fat trial and a mechanistic study in healthy men ^[1][3][4]. For how it differs from the shorter GHRH(1-29) fragment, see tesamorelin vs sermorelin.

What Does Tesamorelin Do?

Tesamorelin binds the GHRH receptor on pituitary somatotrophs (the cells that make growth hormone) and triggers them to synthesize and release growth hormone in the body's natural pulsatile rhythm ^[11]. The released growth hormone drives the liver to produce IGF-1, and together they promote lipolysis — the breakdown of stored fat — preferentially in visceral adipose tissue ^[1].

The headline finding is selectivity. In the pivotal 26-week Phase 3 trial of 412 HIV patients, tesamorelin 2 mg/day reduced visceral fat by 15.2% while placebo rose 5.0%, and it did so without significant change in subcutaneous fat or BMI ^[1]. IGF-1 rose 81.0% and triglycerides fell 50 mg/dL ^[1]. A 2026 meta-analysis of five randomized trials pooled the visceral-fat reduction at -27.7 cm2 and added a -4.28% hepatic-fat-fraction reduction and a +1.42 kg gain in lean mass ^[15]. The full account is on the how tesamorelin works page and in the visceral-fat research.

What Tesamorelin Is Studied For

Tesamorelin's one FDA-approved use is reducing excess abdominal visceral fat in HIV-associated lipodystrophy — a metabolic complication of HIV and antiretroviral therapy in which fat redistributes abnormally and accumulates in the abdomen ^[5]. That is the studied population for every pivotal efficacy result on this site.

Beyond that indication, tesamorelin has been studied as a research endpoint in several off-label areas, none FDA-approved. A JAMA trial measured hepatic fat in HIV patients ^[3]. A 12-month study in obese adults with reduced GH secretion linked the IGF-1 rise to improved muscle phosphocreatine recovery, a marker of mitochondrial function ^[7]. And a mechanistic study in healthy men characterized its effect on GH pulsatility and insulin sensitivity ^[4]. General-population or cosmetic fat loss, anti-aging, and performance use are off-label and are not established by large randomized trials. Common reader questions on these uses are answered in the frequently asked questions.

Is Tesamorelin a Steroid?

No. Tesamorelin is a peptide hormone — a 44-amino-acid GHRH analogue — not an anabolic-androgenic steroid. Steroids are lipid-derived molecules built on a four-ring carbon skeleton; tesamorelin is a chain of amino acids that acts on a cell-surface receptor, not an intracellular steroid receptor ^[4].

It also works one step upstream of growth hormone rather than mimicking testosterone or any sex steroid. It stimulates the pituitary to release the body's own growth hormone, which then raises IGF-1 ^[11]. Sex steroids do modulate GHRH-driven GH output — testosterone roughly doubled GHRH-stimulated pulsatile GH in older men in one study — but that is a separate axis acting on tesamorelin's pathway, not evidence that tesamorelin is itself a steroid ^[8].

Regulatory Status: FDA-Approved for HIV-Associated Lipodystrophy

Tesamorelin is FDA-approved, but narrowly. The agency approved it in November 2010 under NDA 022505 to reduce excess abdominal fat in HIV-infected adults with lipodystrophy ^[5]. That is its only FDA-approved indication. Every other use — general visceral-fat reduction, non-HIV fatty-liver disease, anti-aging, GH optimization, cosmetic or performance use — is off-label, outside the approved indication.

The approval rests on a robust HIV dataset: the 26-week and 52-week Phase 3 program in HIV patients ^[1][2], supported by a JAMA hepatic-steatosis trial ^[3] and the NIH LiverTox monograph, which assigns tesamorelin a likelihood score of E — unlikely to cause clinically apparent liver injury ^[5]. Tesamorelin is also prohibited in sport under the World Anti-Doping Agency Prohibited List (category S2: peptide hormones, growth factors, and mimetics). The material discussed on this site is research-grade tesamorelin supplied for laboratory study, which is not the approved finished drug product and is not for human self-administration. For the side effects and safety record, see the research page.