How Does Tesamorelin Work?

A stabilized GHRH(1-44) analogue

Trial reports describe tesamorelin as a synthetic GHRH(1-44) analogue and as a stabilized analogue of human growth hormone-releasing hormone. It is not growth hormone itself: it is designed to act on the pituitary so that the body's own growth hormone secretion changes, which is why studies track endogenous growth hormone pulses and IGF-1 rather than levels of an external hormone.Human trial · PMID 20943777Human RCT · PMID 23689947

Because growth hormone is associated with side effects including insulin resistance, a 2017 randomized trial in 53 people with type 2 diabetes tested whether this stabilized analogue changed insulin sensitivity or diabetes control over 12 weeks. There were no significant differences between groups in relative insulin response, and fasting glucose and HbA1c at week 12 were not significantly different. No participant discontinued because of loss of diabetes control.Human RCT · PMID 28617838

From the pituitary to IGF-1

The mechanism was measured directly in a 2011 study of 13 healthy men. Over two weeks, mean overnight growth hormone rose (P = 0.004), as did the average growth hormone peak area (P = 0.001) and basal growth hormone secretion (P = 0.008), measured by frequent overnight sampling. IGF-1 rose significantly (P < 0.0001). The authors concluded that tesamorelin augments both basal and pulsatile secretion of the body's own growth hormone.Human trial · PMID 20943777

In the same study, neither fasting glucose (P = 0.93) nor glucose uptake during a euglycemic hyperinsulinemic clamp (P = 0.61) changed significantly. This matters because growth hormone itself is known for effects on glucose handling; in this short study, IGF-1 rose while peripheral glucose uptake under the clamp appeared preserved.Human trial · PMID 20943777

Why study it in HIV? A 2013 review describes suppression of pituitary growth hormone production in HIV lipodystrophy, linked to increased somatostatin tone, decreased ghrelin and increased free fatty acids, alongside complications such as chronic inflammation, insulin resistance and lipid abnormalities. A GHRH analogue acts upstream of that suppressed pituitary output.Review · PMID 23657561

Randomized trials: visceral adipose tissue responses

A randomized, placebo-controlled trial enrolled 412 people with HIV (86% male) who had documented abdominal fat accumulation while on antiretroviral medications. Participants received either tesamorelin or placebo for 26 weeks. The primary measure was the percent change from baseline in visceral adipose tissue (VAT) area shown on computed tomography. Secondary measures included triglyceride levels, total cholesterol to HDL-cholesterol ratio, IGF-1 concentration, and glucose metabolism markers.Human RCT · PMID 18057338

Visceral adipose tissue declined 15.2% from baseline in the tesamorelin group, while placebo participants experienced a 5.0% increase (P<0.001). Triglyceride concentrations fell in the tesamorelin group and rose in placebo. The ratio of total cholesterol to HDL-cholesterol decreased 0.31 in tesamorelin participants versus an increase of 0.21 in placebo. IGF-1 levels rose 81.0% in the tesamorelin group and fell 5.0% in placebo (P<0.001). Glucose and insulin levels showed no significant differences between groups.Human RCT · PMID 18057338

Extension trial: long-term visceral adiposity reduction

A follow-up randomized trial examined tesamorelin in 404 people with HIV and abdominal fat accumulation while on antiretroviral medications. The study consisted of two sequential phases: a 6-month efficacy phase with randomization to tesamorelin or placebo (2:1 ratio), followed by a 6-month extension phase. In the extension, those initially assigned to tesamorelin were re-randomized to continue or switch to placebo, while those initially on placebo switched to active assignment.Human RCT · PMID 20101189

Visceral adipose tissue declined 10.9% from baseline (−21 cm²) in the tesamorelin group versus 0.6% (−1 cm²) in placebo at 6 months (P < 0.0001). Trunk fat and waist-hip ratio also fell, with no change in limb fat or abdominal fat below the skin. Insulin-like growth factor-1 rose significantly (P < 0.001), but fasting glucose and insulin levels showed no change. Participants rating their belly appearance distress reported significant change in the tesamorelin group (P = 0.02) compared to placebo. Continuing tesamorelin for 12 months produced an approximately 18% reduction in VAT (P < 0.001), while those who switched from tesamorelin to placebo experienced rapid loss of initial findings.Human RCT · PMID 20101189

Hepatic fat fraction and liver histology in HIV-associated NAFLD

Non-alcoholic fatty liver disease (NAFLD) affects a substantial proportion of people with HIV and represents a cause of morbidity and mortality risk in this population. A randomized, double-blind trial examined tesamorelin in 61 people with HIV and NAFLD (hepatic fat fraction ≥5% measured by magnetic resonance spectroscopy). Participants were assigned 1:1 to tesamorelin or placebo for 12 months, followed by a 6-month open-label phase in which all received tesamorelin.Human RCT · PMID 31611038

Hepatic fat fraction showed a difference between tesamorelin and placebo groups (p=0.018), with a relative reduction of approximately 37% from baseline in the tesamorelin group compared to placebo. After 12 months, 35% of tesamorelin-assigned participants and 4% of placebo participants achieved a hepatic fat fraction below 5% (p=0.0069). Changes in fasting glucose and glycated hemoglobin showed no difference between groups at 12 months. Participants in the tesamorelin group reported more localized site-specific complaints than placebo, but none were classified as serious.Human RCT · PMID 31611038

Molecular mechanisms: inflammatory and fibrogenic pathway suppression

Proteomic analysis of plasma samples from the hepatic fat trial revealed that tesamorelin reduced key inflammatory and tissue-repair pathway markers. Tesamorelin produced significant changes in vascular endothelial growth factor A (VEGFA, log2-fold change −0.20 ± 0.35 versus 0.05 ± 0.34 for placebo, P = 0.02), transforming growth factor beta 1 (TGFB1, −0.35 ± 0.56 versus −0.05 ± 0.43, P = 0.05), and macrophage colony-stimulating factor 1 (CSF1, −0.17 ± 0.21 versus 0.02 ± 0.20, P = 0.004). These proteins are involved in angiogenesis, fibrogenesis, and monocyte recruitment.Human trial · PMID 34006921

Among tesamorelin-assigned participants, reductions in VEGFA correlated with decline in NAFLD activity score (r = 0.62, P = 0.006), and CSF1 reductions associated with NAFLD activity decline (r = 0.50, P = 0.04). Decreases in TGFB1 and CSF1 linked to reduced gene-level fibrosis score (r = 0.61, P = 0.009 and r = 0.64, P = 0.006, respectively). These findings indicate that tesamorelin's effects on liver fat coexist with suppression of inflammatory and fibrogenic mediators, possibly through down-regulation of hepatic gene sets involved in inflammation, tissue repair, and cell proliferation.Human trial · PMID 34006921

Metabolic and mitochondrial function markers

In a 12-month randomized trial in 39 obese adults with reduced GH secretion, tesamorelin produced significantly greater changes in IGF-1 than placebo (P = 0.02). Changes in IGF-1 from tesamorelin correlated with alterations in phosphocreatine recovery, a marker of mitochondrial oxidative capacity measured by magnetic resonance spectroscopy after submaximal exercise. The association was stronger among tesamorelin-assigned participants alone (r = 0.71, P = 0.03) and remained significant after adjusting for age, sex, body composition, and insulin sensitivity markers.Human RCT · PMID 24178787

Meta-analysis: body composition and lipid effects across trials

A meta-analysis of four randomized controlled trials encompassing 909 people with HIV-associated lipodystrophy found that tesamorelin produced consistent effects on body composition. Visceral adipose tissue showed a mean difference of −21.47 cm² (95% CI −34.73, −8.22, P = 0.002; I² = 74%). Waist circumference changed by −1.61 cm (95% CI −2.28, −0.95, P < 0.00001; I² = 0%). Trunk fat showed a mean difference of −1.20 kg (95% CI −1.47, −0.93, P < 0.00001; I² = 0%). Lean body mass showed a mean difference of 1.42 kg (95% CI 1.13, 1.71, P < 0.00001; I² = 0%). Total cholesterol showed a mean difference of −0.16 mmol/L (95% CI −0.27, −0.06, P = 0.003; I² = 0%).Meta-analysis · PMID 42538058

Adverse events and safety considerations

In the 26-week trial, reported adverse events showed no significant difference between tesamorelin and placebo groups overall. However, more participants in the tesamorelin group withdrew due to reported adverse events. In the 12-month hepatic fat trial, participants assigned to tesamorelin reported more localized site-specific complaints than those on placebo, though none were serious. The meta-analysis reported growth hormone-related adverse effects and a higher discontinuation rate (risk ratio 2.25, 95% CI 0.98, 5.17, P = 0.06), an interval that includes no difference. The 12-month trials showed no change in glucose metabolism or significant differences in fasting glucose and glycated hemoglobin between tesamorelin and placebo.Human RCT · PMID 18057338Human RCT · PMID 20101189Human RCT · PMID 31611038Meta-analysis · PMID 42538058

The studies at a glance

Randomized trials of tesamorelin in HIV-associated lipodystrophy and NAFLD

Frequently asked questions