Short answer: Both copy GHRH, the brain signal that tells the pituitary to release growth hormone. Sermorelin is the first 29 amino acids;1 tesamorelin is the full 44-amino-acid sequence with an added fatty chain.2 Tesamorelin (Egrifta) is FDA approved only to reduce belly fat in adults with HIV lipodystrophy. Sermorelin was approved as Geref, then discontinued, not for safety reasons.3
| Sermorelin | Tesamorelin (Egrifta) | |
|---|---|---|
| What it is | GHRH(1-29)-NH2, the first 29 amino acids of GHRH1 | The full 44-amino-acid GHRH sequence with a hexenoyl (C6) group on the first amino acid2 |
| Approval status | Approved as Geref (diagnostic 1990; children with GH deficiency 1997); approvals withdrawn June 2009 after discontinuation; FDA found this was not for safety or effectiveness3 | FDA approved since 20102 |
| Approved use | None current. Geref was for idiopathic GH deficiency in children and for testing pituitary GH release3 | Reducing excess abdominal fat in adults with HIV and lipodystrophy; not for weight loss2 |
| Label dose | No current label | Egrifta WR: 1.28 mg under the skin once daily. Egrifta SV: 1.4 mg once daily. The two are not interchangeable24 |
| Half-life | About 4.3 minutes during and after an IV infusion in 10 men1 | 11 minutes (WR) and 8 minutes (SV) after one injection under the skin24 |
| Time to peak (Tmax) | No confirmed value under the skin | 0.15 hours (about 9 minutes)2 |
| Pivotal trials | No current label trial data | Two 26-week trials: visceral fat −18% vs +2% on placebo, and −14% vs −2%2 |
| Key label warnings | No current label | Raised IGF-1, fluid retention, glucose intolerance; not for use in pregnancy or active cancer2 |
| Sport | WADA S2.2.4 (named)5 | WADA S2.2.4 (named)5 |
Natural GHRH is 44 amino acids long. Sermorelin keeps only the first 29 and is cleared within minutes: in a 1994 infusion study its half-time in the blood was about 4.3 minutes.1 Tesamorelin keeps all 44 amino acids and adds a short fatty chain at the front end.2 Even so, its label half-life under the skin is only 8 to 11 minutes, so both are short-acting signals given daily rather than long-acting drugs.42
The Egrifta label rests on two randomized trials in adults with HIV and excess belly fat (412 and 404 people). After 26 weeks of 2 mg daily (the original formulation), visceral fat measured by CT fell 18% vs a 2% rise on placebo in Study 1, and 14% vs 2% in Study 2.2 The label says it is not for weight loss because it is weight neutral, and long-term heart safety has not been established.2
Sermorelin has no comparable modern trial. Its approvals covered children with GH deficiency and a diagnostic test, and were withdrawn in 2009 after the maker stopped selling it. FDA later found that was not for safety or effectiveness reasons.3 A 2026 review notes that its use for body composition in healthy adults rests on limited, indirect evidence.6 No trial has compared the two directly.