Tesamorelin and sermorelin are both synthetic analogs of GHRH (growth hormone-releasing hormone). Sermorelin is the first 29 amino acids of native GHRH; tesamorelin is the same 29-amino-acid backbone with an N-terminal trans-3-hexenoyl modification that resists DPP-4 enzymatic degradation and extends half-life. Tesamorelin remains FDA-approved as Egrifta for HIV-associated lipodystrophy with documented visceral-fat reduction; sermorelin's FDA approval (Geref) was withdrawn in 2008 for commercial rather than safety reasons. Both stimulate pulsatile endogenous GH release, but tesamorelin's longer half-life produces a sharper pharmacological signal in research-protocol use.
Same backbone, different modifications
Both tesamorelin and sermorelin are synthetic analogs of GHRH (growth hormone-releasing hormone) based on the first 29 amino acids of native GHRH. The difference is one chemical modification.
Sermorelin is the unmodified GHRH 1-29 fragment. Half-life ~12 minutes. The pituitary receives a short pulse of GHRH-receptor stimulation and releases endogenous GH.
Tesamorelin has an N-terminal trans-3-hexenoyl modification that resists DPP-4 enzymatic degradation. Half-life extends to ~26 minutes — still pulsatile but sharper than sermorelin. The pharmacological GH signal per injection is larger.
Regulatory status
| Aspect | Sermorelin | Tesamorelin |
|---|---|---|
| FDA status (current) | Approval withdrawn 2008 | Approved (Egrifta) |
| Approved indication | Pediatric GH deficiency (former) | HIV-associated lipodystrophy |
| Withdrawal reason | Commercial (not safety) | N/A |
| 503A compounding availability | Yes, widespread | Yes, widespread |
| Research-peptide availability | Yes | Yes |
Tesamorelin is the only GHRH analog with current FDA approval in the US. Sermorelin's 2008 withdrawal was a commercial decision by Merck Serono after Genentech-related manufacturing complications, not a safety action.
Clinical evidence (where it exists)
Tesamorelin has the strongest published body-composition data of any GHRH analog. The Egrifta pivotal trials in HIV-associated lipodystrophy showed approximately 15-18% reduction in visceral adipose tissue (measured by CT or MRI) over 26 weeks. The effect was dose-dependent and reversible on discontinuation. IGF-1 elevation was modest and stayed within reference ranges in most patients.
Sermorelin clinical evidence is concentrated in the pediatric GH-deficiency context where it was approved. Adult research-protocol evidence is thinner and most data comes from the time period before Geref's withdrawal.
Research-protocol dosing patterns
| Compound | Typical research protocol dose | Cadence |
|---|---|---|
| Sermorelin | 100-500 mcg subcutaneous | Daily, evening |
| Tesamorelin | 1-2 mg subcutaneous | Daily, evening |
| Tesamorelin (Egrifta) | 2 mg subcutaneous | Daily, FDA-indicated |
The bedtime cadence for both is chosen to align with the natural overnight GH pulse. Tesamorelin's higher absolute dose reflects its different molecular weight and pharmacology — the molar comparison is closer than the milligram comparison suggests.
Cost comparison
- Tesamorelin pharmaceutical (Egrifta): $5,000+ per month retail
- Tesamorelin compounded (503A): $300-600 per month
- Sermorelin compounded (503A): $80-200 per month
- Research-grade tesamorelin: significantly lower, but not labeled for human use
- Research-grade sermorelin: lowest price point, same caveat
The cost gap is one of the most consistent reasons research protocols cite sermorelin rather than tesamorelin when either would work for the protocol's goal.
Side effect profile
Both compounds share the GH-axis side effect set: edema, joint pain, paresthesias, insulin resistance with chronic dosing, and elevated IGF-1 with potential effects on existing neoplasia. Tesamorelin's longer-duration GH pulse produces a slightly more pronounced version of each effect, but they are qualitatively the same.
Neither has the prolactin or cortisol elevation that older GH secretagogues produced. Neither carries the cardiac-rhythm signal that occasionally appears with non-selective ghrelin agonists like GHRP-6.
What this comparison does NOT settle
Long-term healthspan vs short-term outcomes. All published trials are short-term (typically 6-12 months). Whether either compound improves healthspan or lifespan over decades of use is not yet measurable.
Optimal dose for healthy adults. The FDA-approved tesamorelin dose is for HIV-associated lipodystrophy specifically. Whether the same dose is optimal for healthy adult research-protocol use is an open question.
Combination with ghrelin agonists. The most common stack pattern in research protocols pairs a GHRH analog (typically sermorelin or CJC-1295) with a ghrelin-receptor agonist (typically ipamorelin). Tesamorelin in similar stacks is less common; the longer half-life changes the kinetic logic of the pair.
Related reading
- Sermorelin peptide page — the deeper sermorelin reference.
- Tesamorelin peptide page — the deeper tesamorelin reference.
- CJC-1295 vs Ipamorelin — the most-paired GH-axis stack pattern.
- Longevity peptides 2026 — where the GH-axis cluster sits in the broader longevity landscape.
Sources
- Falutz J et al. Effects of tesamorelin (TH9507), a growth hormone-releasing factor analog, in HIV-infected patients with excess abdominal fat. J Clin Endocrinol Metab 2007.
- Stanley TL et al. Reduction in visceral adiposity is associated with an improved metabolic profile in HIV-infected patients receiving tesamorelin. AIDS 2014.
- Walker RF. Sermorelin: a better approach to management of adult-onset growth hormone insufficiency. Clin Interv Aging 2006.
- FDA Drug Approval Package — Egrifta (tesamorelin) 2010.
Frequently asked
What's the main difference between tesamorelin and sermorelin?
Both are GHRH analogs based on the same 29-amino-acid backbone, but tesamorelin has an N-terminal modification that resists DPP-4 enzymatic degradation and extends half-life from sermorelin's ~12 minutes to ~26 minutes. Tesamorelin produces a sharper, more sustained GH pulse per injection. Tesamorelin is FDA-approved (Egrifta) for HIV-associated lipodystrophy; sermorelin (Geref) was withdrawn in 2008 for commercial reasons.
Which one is FDA-approved?
Tesamorelin is currently FDA-approved as Egrifta for HIV-associated lipodystrophy, with documented visceral-fat reduction of approximately 15-18% in pivotal trials. Sermorelin was FDA-approved as Geref in 1990 for pediatric GH deficiency but voluntarily withdrawn in 2008 - the withdrawal was commercial, not safety-related. Both remain available through 503A compounding pharmacies.
Which one is better for body composition?
Tesamorelin has the only FDA-recognized body-composition indication. The Egrifta trials in HIV-associated lipodystrophy showed approximately 15-18% reduction in visceral adipose tissue over 26 weeks. Sermorelin's body-composition evidence in research protocols is weaker because the very short half-life (~12 min) produces a smaller per-injection GH pulse. Research protocols pursuing body-composition outcomes more often cite tesamorelin than sermorelin.
What's the cost difference?
Tesamorelin pharmaceutical-grade (Egrifta) lists at over $5,000 per month at retail. 503A compounded tesamorelin runs in the $300-600/month range. Sermorelin via 503A typically runs $80-200/month. Research-peptide vendor pricing is significantly lower for both, but for non-human-use research only.
Are tesamorelin and sermorelin safe to combine?
They target the same receptor (GHRHR) and produce similar downstream effects. Combining the two is uncommon in research-protocol literature because the receptor saturates with one or the other; the second compound is largely redundant. Combining a GHRH analog (either tesamorelin or sermorelin) with a ghrelin receptor agonist like ipamorelin is the more common stack pattern because the two activate different receptors.