Here's the short version. Tesamorelin is a belly-fat drug for adults with HIV, sold only as the brand Egrifta. Its trials picked up a small rise in lean mass. That's a long way from building muscle, and these results do not establish a muscle-building benefit in people without HIV [6].
The full older-adult cognition paper also reports a 3.7% increase in DXA lean tissue over 20 weeks, alongside reduced body fat. This is a body-composition result, not a demonstration of improved muscle strength [4].
Lean mass rose about 2.6 lb (1.2 kg) in the trials, in adults with HIV
The trials behind the approval measured lean body mass as a secondary result. Over 26 weeks it rose 2.9 lb (1.3 kg) in one study and 2.6 lb (1.2 kg) in the other on tesamorelin. On placebo it fell 0.4 lb (0.2 kg) and 0.07 lb (0.03 kg) [6].
That's a little under 3 pounds on the drug. Lean body mass counts everything that isn't fat, water included. The label lists fluid retention as a known side effect, so part of a lean-mass gain could be water rather than muscle. The trials didn't separate the two.
The only muscle-specific look came later. Researchers went back to CT scans from the same two trials and measured four trunk muscle groups [1]. Among people on tesamorelin whose deep belly fat fell at least 8%, lean muscle area rose 0.10 to 0.17 square inches (0.64 to 1.08 cm²) more than on placebo. Total area of the rectus and psoas muscles rose about 0.07 square inches (0.44 and 0.46 cm²) each. Muscle density went up too, which suggests less fat inside the muscle.
The muscle numbers come only from people the drug already worked for
A responder-only comparison can favor treatment and does not preserve the full randomized comparison. The authors called their analysis exploratory, and they left non-responders out on purpose [1].
So the honest reading runs like this. If tesamorelin shrinks your belly fat, it may also nudge trunk muscle a little. If it doesn't, those numbers don't describe you. The trial population was 87% men, all with HIV and extra abdominal fat.
| Claim | Human evidence | Result | Strength of evidence |
|---|---|---|---|
| Adds lean mass | Egrifta's two phase 3 trials, adults with HIV, 26 weeks [6] | +2.9 and +2.6 lb (+1.3 and +1.2 kg) vs −0.4 and −0.07 lb (−0.2 and −0.03 kg) on placebo | Moderate, in HIV only; water not separated from muscle |
| Builds trunk muscle | Adrian 2019: 193 responders vs 148 on placebo, HIV, 26 weeks [1] | Lean area +0.10 to 0.17 square inches (0.64 to 1.08 cm²) in four trunk muscle groups | Low: exploratory, responders only |
| Reduces deep belly fat | Falutz 2007, 412 adults with HIV [2] | −15.2% vs +5.0% on placebo | High, in HIV |
| Raises IGF-1 | Falutz 2007 [2] | +81% vs −5% on placebo | High |
| Improves strength or performance | Not measured in the trials behind the label | No data | None |
| Changes body composition in healthy adults | Baker 2012: 152 adults aged 55 to 87, 20 weeks [4] | Body fat −7.4%; DXA lean tissue +3.7%; not a strength or athletic performance result | Low for muscle |
Egrifta is approved to shrink belly fat in HIV, not to build muscle
Egrifta is approved to reduce excess abdominal fat in adults with HIV-associated lipodystrophy. Its label also says it isn't for weight-loss management and that long-term heart safety hasn't been established [5]. In the pooled trials, the fat that shrank was the deep kind around the organs; fat under the skin barely moved [3].
There's no compounded version to fall back on. Since March 2020, FDA has treated Egrifta as a biologic, which can't be compounded, so the brand is the one legal route. The details are in whether you can get tesamorelin legally, and what it costs is in our tesamorelin cost guide.
Tesamorelin raises IGF-1 sharply, and the label watches for that
Tesamorelin is a man-made version of growth-hormone-releasing hormone. It signals the pituitary to release more growth hormone, which drives IGF-1. In the main approval trial, IGF-1 rose 81% on tesamorelin and fell 5% on placebo [2].
IGF-1 is the hormone people chasing muscle care about. It's also the one the label flags. The effects of long-term high IGF-1 are unknown, so prescribers check it during treatment and may stop the drug if it stays high [5].
- Fluid retention: swelling, joint pain and carpal tunnel syndrome.
- Blood sugar: HbA1c reached 6.5% or higher in 5% of people on the drug versus 1% on placebo by week 26.
- Allergy: rash, itching, flushing or hives in 4% in clinical trials.
- Cancer history: it's ruled out with active cancer and stopped if cancer comes back.
Adding a second growth-hormone drug on top is a question for a prescriber, not a forum. More on that combination in tesamorelin and ipamorelin together.
A trial in muscle wasting stopped after three people
The one trial built to test tesamorelin on muscle loss enrolled three people. It studied adults with COPD and muscle wasting, started in September 2011 and ended that December [7].
The trial listing gives the reason as a corporate decision unrelated to safety. Three people can't answer a muscle question either way, so it adds nothing to the evidence.
Tesamorelin is banned in tested sport
If you compete in a tested sport, the answer is simple. The World Anti-Doping Agency's 2026 Prohibited List names tesamorelin among growth hormone releasing factors in class S2, banned at all times [8].
Growth hormone releasing factors, including, but not limited to: growth hormone-releasing hormone (GHRH) and its analogues (e.g. CJC-1293, CJC-1295, sermorelin and tesamorelin)[8]
Outside sport, the vials sold for "research use" aren't a legal route to the drug. That holds whatever the goal. How fast the approved effects show up is covered in how long tesamorelin takes to work.
For a muscle goal, start with options that were tested for it
If muscle or a leaner build is the goal, tesamorelin isn't the tool its label describes. Start with our body composition shortlist, which sorts the legal prescription options by goal.
Thinking of sermorelin instead? It's the closest relative and is prescribed as a compounded drug. Its muscle record is thin too, as does sermorelin build muscle lays out. Ask your prescriber what was actually measured before you start anything.