Tesamorelin (Egrifta): A Different Axis, A Narrower Licence

The short version

Tesamorelin (Egrifta) does not belong to the same drug family as the other three compounds on this desk. It does not touch a gut-hormone receptor and it is not an appetite drug.

Instead it works on the pituitary, the small gland at the base of the brain that releases growth hormone. Tesamorelin is a synthetic copy of the signal that tells the pituitary to release it. More growth hormone means more IGF-1 from the liver, and together those two break down fat — preferentially the deep fat packed around the internal organs rather than the fat under the skin.

That matters because the two kinds of fat behave differently. Deep visceral fat is the kind linked to liver disease and metabolic problems, and it is not what a bathroom scale measures. Tesamorelin's trials measure it by imaging.

Its approval is narrow: one condition, HIV-associated lipodystrophy, and nothing else. Every other use is off-label. Its effect also reverses within weeks of stopping. This page reports published research and recommends nothing.

What it is

Tesamorelin is a synthetic 44-amino-acid analogue of human growth hormone-releasing hormone — GHRH(1-44)-NH2 — carrying a trans-3-hexenoic acid group conjugated to the N-terminus. Empirical formula of the free base C221H366N72O67S; it is supplied clinically as the acetate salt.

The N-terminal modification is the whole point of the molecule. Native GHRH is cleaved rapidly by dipeptidyl peptidase-IV; the hexenoyl group blocks that cleavage and extends plasma stability. In the literature it also appears as TH9507 and as trans-3-hexenoyl-GHRH(1-44) amide.

Its class is growth hormone-releasing hormone receptor agonist. Its regulatory position is unusually specific: approved in the United States in November 2010 under NDA 022505 to reduce excess abdominal fat in adults with HIV-associated lipodystrophy ^[18], and marketed under the brand name Egrifta. There is no approved indication outside that one, and no second brand name, because there is no second indication for one to attach to. General visceral-fat reduction, anti-ageing use, cognitive enhancement and non-HIV fatty liver disease are all off-label and investigational.

One further status note that does not apply to any other compound on this desk: tesamorelin is prohibited in sport under the World Anti-Doping Agency Prohibited List category S2 — peptide hormones, growth factors, related substances and mimetics — both in and out of competition.

How it works

Tesamorelin binds the growth hormone-releasing hormone receptor on anterior-pituitary somatotroph cells. That activates the Gs/adenylyl-cyclase/cAMP/PKA cascade and stimulates both synthesis and pulsatile secretion of the body's own growth hormone.

The word pulsatile carries real weight. Growth hormone is not released continuously; it comes in bursts, mostly overnight, and the pattern of release appears to matter as much as the total amount. Because tesamorelin amplifies an existing rhythm rather than supplying exogenous hormone at a flat concentration, its metabolic profile differs from that of recombinant growth hormone — most consequentially with respect to insulin sensitivity.

Downstream, the released growth hormone drives hepatic production of insulin-like growth factor-1 (IGF-1). Growth hormone and IGF-1 together promote lipolysis, and they do so preferentially in visceral adipose tissue rather than subcutaneous fat. That tissue selectivity is why the endpoint in its trials is a cross-sectional visceral fat area measured by imaging rather than a number on a scale.

The pharmacology was demonstrated directly. In 13 healthy men receiving 2 mg daily for two weeks, mean overnight growth hormone rose by 0.5 µg/L (P=0.004) and IGF-1 rose by 181 µg/L (P<0.0001), while neither fasting glucose (P=0.93) nor insulin-stimulated glucose uptake (P=0.61) was significantly affected ^[20]. That last pair of results is the clinically interesting part: the growth-hormone axis was stimulated without measurable degradation of insulin sensitivity over that period.

Mechanistic targets: anterior-pituitary somatotrophs via the GHRH receptor; visceral adipose tissue (lipolysis); liver (IGF-1 synthesis and hepatic fat); the GH/IGF-1 axis as a whole.

What the trials show

The evidence base is narrow in population and consistent in result.

Pooled randomised evidence. A 2026 meta-analysis of five randomised controlled trials in HIV-associated lipodystrophy found tesamorelin reduced visceral adipose tissue by a mean difference of -27.71 cm² (95% CI -38.37 to -17.06; P<0.001), reduced trunk fat by -1.18 kg, and reduced hepatic fat fraction by -4.28%, while increasing lean body mass by +1.42 kg — all at P<0.001, and without serious adverse events ^[17].

That lean-mass result is worth pausing on. Every other compound on this desk loses lean mass alongside fat. This one adds it. The mechanisms are entirely different, and so are the body-composition consequences.

A representative randomised trial. A six-month trial in 50 antiretroviral-treated adults with HIV — 28 on tesamorelin, 22 on placebo, at 2 mg daily — produced a treatment effect of -42 cm² in visceral fat (P=0.005) and reduced the hepatic lipid-to-water percentage by a net -2.9% (P=0.003) ^[19].

Durability, and its limit. The 52-week programme compared 2 mg daily in 273 participants against placebo in 137. Visceral fat reduction was sustained at -18% over 52 weeks (P<0.001 against baseline), and changes in glucose parameters over that year were not clinically significant. Critically, visceral fat reaccumulated on discontinuation ^[21]. The benefit is contingent on continued administration.

Liver safety. The NIH LiverTox monograph assigns tesamorelin a likelihood score of E — unlikely to cause clinically apparent liver injury — noting no reported attributable cases of liver injury and no de novo serum-enzyme elevations in trials ^[18].

What to watch: cautions and open controversies

A note on what is absent before what is present: the signed research record behind this page carries no community-report set and no compiled safety-caution list for tesamorelin, unlike the three incretin compounds. Rather than fill that gap with material invented for the purpose, this section reports only what the record actually contains. There is no anecdotal section on this page for that reason.

What the record does document is a set of live controversies and limits:

• The approval is narrow and everything else is off-label. Approval covers excess abdominal fat in HIV-associated lipodystrophy ^[18]. General visceral-fat reduction in people without HIV, anti-ageing use, cognitive enhancement and non-HIV fatty liver disease are all outside it.
• The trial population is specific. Pivotal efficacy trials were conducted in HIV-positive adults on antiretroviral therapy ^[17][19][21]. Generalising those results to people without HIV is mechanistically plausible — the GHRH receptor does not know a patient's serostatus — but it is not established by large randomised trials, and mechanistic plausibility has repeatedly failed to survive contact with an actual endpoint trial.
• The effect is contingent on continued use. Visceral fat reaccumulates within weeks of stopping ^[21]. This is not a course of treatment with a durable result; it is ongoing therapy for as long as the effect is wanted.
• IGF-1 elevation and oncologic safety. Stimulating the growth-hormone axis raises serum IGF-1 ^[20], and IGF-1 is a growth factor. Trials showed no excess malignancy signal over 52 weeks ^[21], but long-term oncologic safety data are limited, and active malignancy is a labelled contraindication. This is a genuine open question rather than a resolved one in either direction.
• Glucose handling. Modest glucose perturbation can occur, and monitoring is warranted in people with prediabetes or dysglycaemia. The counterweight is substantial: insulin-stimulated glucose uptake was not significantly affected in healthy men over two weeks ^[20], glucose changes over 52 weeks were not clinically significant ^[21], and a dedicated trial in type 2 diabetes found no significant change in glycated haemoglobin.
• Cognitive findings are mixed. A non-HIV ageing trial showed an executive-function benefit; a 2025 trial in HIV cognition did not show significant neurocognitive improvement over standard care. Two results pointing different ways is the current state, not a consensus.
• Prohibited in sport. WADA category S2, in and out of competition. Any athlete subject to testing should treat that as decisive.
• Access and material quality. High pharmaceutical cost and injection-only administration limit access to the approved product. Research-grade material sold for laboratory use lacks the purity and potency oversight the approved product carries, and none of the trial data above describes it.

What remains unknown

Whether it works the same way outside HIV. This is the largest gap, and it is the one most often glossed over when tesamorelin is discussed as a general visceral-fat agent. The mechanism does not obviously depend on HIV or antiretroviral therapy, but antiretroviral-associated lipodystrophy is a distinctive metabolic state, and the trial record does not extend beyond it in any large randomised form.

Long-horizon IGF-1 safety. A 52-week trial cannot answer an oncologic question that operates on a decade-scale. The absence of a signal over a year is reassuring and is not the same as a demonstrated absence of risk ^[21].

What the hepatic-fat result means clinically. Reductions in hepatic fat fraction are documented in both the pooled analysis ^[17] and individual trials ^[19]. Whether that translates into histological improvement or into hard liver outcomes has not been established here — the same gap that applies to retatrutide's much larger liver-fat result ^[14].

Cognition. Mixed, as above, and unresolved.

Where it fits in metabolic research

Tesamorelin is on this desk as the control case. It answers a metabolic question that overlaps the incretins' — where is fat stored, and can it be moved — by a route that shares no receptor, no hormone family and no side-effect profile with them.

That produces three instructive contrasts. It adds lean mass where the incretins subtract it ^[17]. It targets visceral fat specifically where the incretins reduce total body weight and take visceral fat along with everything else. And it produces no appetite effect at all, which means its result is not an intake result — a distinction that separates it from semaglutide and tirzepatide as sharply as retatrutide's glucagon arm does, though in the opposite direction.

The convergence point is the liver. Two mechanisms with nothing in common — the growth-hormone axis here ^[17][19], triple incretin agonism there ^[14] — both reduce hepatic fat substantially. That is either a coincidence of two drugs that reduce adiposity generally, or a hint that hepatic fat is downstream of several independent levers. The literature has not settled which, and the comparison page sets the four side by side without pretending it has.