Quick answer: Sermorelin, tesamorelin, and ipamorelin are three short peptides that all end up in growth-hormone-axis research, but they don’t act through the same receptor. Sermorelin and tesamorelin are growth-hormone-releasing hormone (GHRH) analogs. Ipamorelin is a growth-hormone-releasing peptide (GHRP) that acts through the ghrelin receptor. Tesamorelin is the only one of the three that is FDA-approved, sold as Egrifta for HIV-associated lipodystrophy. Velora supplies all three as research compounds for in-vitro work.
Research use only: what this article is, and what it isn’t
This article is a mechanism-focused comparison of three growth-hormone-axis peptides, written for researchers selecting reference compounds for in-vitro or preclinical work. It is not medical advice, and it is not a prescribing or self-administration guide.
Tesamorelin is FDA-approved as Egrifta (and Egrifta SV, a more concentrated formulation) for the specific indication of HIV-associated lipodystrophy in adult patients with excess abdominal fat. That approved product is a prescription medication supplied through controlled clinical channels. The tesamorelin Velora sells as a 10 mg research vial is a research-grade material for laboratory use, not the approved drug, and is not intended for human or veterinary use under any framing.
Sermorelin and ipamorelin are not FDA-approved as drugs for any indication. (Sermorelin previously had an FDA-approved formulation, Geref, that was discontinued from the U.S. market in 2008; it is no longer an approved drug in the United States.) The Velora research-grade material for both peptides is supplied for in-vitro research only. Researchers handling any of these compounds are responsible for compliance with applicable law, including the Federal Food, Drug, and Cosmetic Act (21 U.S.C. § 331, § 355, § 360bbb-3), and institutional review requirements.
The mechanism that separates them
The primary mechanistic distinction to keep straight is that these three peptides act on two different receptors.
GHRH (growth-hormone-releasing hormone) is the hypothalamic hormone that signals the anterior pituitary to release growth hormone. Sermorelin and tesamorelin are GHRH-receptor agonists. They act as agonists at the GHRH receptor by mimicking endogenous GHRH signaling.
GHRPs (growth-hormone-releasing peptides) are a separate class that act on a different receptor entirely: the ghrelin receptor (GHSR-1a), which sits on the same pituitary cells. Ipamorelin is a selective GHRP. It is not a GHRH analog. The two classes can be studied separately or in combination because they engage independent pathways that converge on growth-hormone secretion.
| Compound | Class | Receptor | Sequence basis | FDA status |
|---|---|---|---|---|
| Sermorelin | GHRH analog | GHRH receptor | Native GHRH 1-29 | Not approved (Geref discontinued 2008) |
| Tesamorelin | Stabilized GHRH analog | GHRH receptor | GHRH 1-44 with N-terminal trans-3-hexenoic acid modification | Approved (Egrifta / Egrifta SV, HIV lipodystrophy) |
| Ipamorelin | GHRP (selective) | Ghrelin receptor (GHSR-1a) | Synthetic pentapeptide | Not approved |
Sermorelin, in research terms
Sermorelin is a synthetic peptide corresponding to the first 29 amino acids of native GHRH, which is the smallest fragment that retains full biological activity at the GHRH receptor. The molecular weight is approximately 3,358 daltons. Its half-life in circulation is short, on the order of 10 to 20 minutes, which is why historical clinical use relied on bedtime administration in pediatric growth-hormone studies, mimicking the natural nocturnal GHRH pulse.
The published research base on sermorelin sits mostly in the pediatric endocrinology literature from the 1980s and 1990s, when it was used as a diagnostic and treatment tool for growth-hormone deficiency in children. The FDA-approved formulation Geref was withdrawn from the U.S. market in 2008 for commercial rather than safety reasons, and sermorelin has not been a U.S. approved drug since. For benchwork, sermorelin is the GHRH-receptor reference compound when you need a peptide that mirrors the native ligand sequence directly.
Tesamorelin, in research terms
Tesamorelin is the same GHRH backbone but engineered for stability. It uses the longer GHRH 1-44 sequence rather than the 1-29 fragment, and it has a trans-3-hexenoic acid modification on the N-terminus that significantly extends the half-life by resisting cleavage by dipeptidyl peptidase IV. The reported half-life is approximately 26 minutes in healthy adults, much longer than sermorelin’s. The molecular weight is approximately 5,135 daltons.
Tesamorelin was approved by the FDA in 2010 as Egrifta for the specific indication of reduction in excess abdominal fat in HIV-infected patients with lipodystrophy. The pivotal Phase 3 data was published in NEJM in 2007 by Falutz and colleagues, reporting significant reductions in visceral adipose tissue and improvements in IGF-1 over 26 weeks at 2 mg subcutaneously daily (Falutz et al., NEJM, 2007).
Because the approved use targets visceral adiposity specifically, tesamorelin is the GHRH analog that turns up most often in body-composition research literature. That research framing is distinct from the broader marketing context the compound shows up in elsewhere. For research use, tesamorelin is the comparator when the question is GHRH-receptor agonism with a usable in vivo half-life.
Ipamorelin, in research terms
Ipamorelin is a synthetic pentapeptide originally characterized by Raun and colleagues at Novo Nordisk in 1998 (Kirsten Raun et al., 1998).. Its distinguishing feature in the GHRP class is selectivity: it stimulates growth-hormone release through the ghrelin receptor with substantially less stimulation of cortisol, prolactin, and ACTH than earlier GHRPs like GHRP-6 caused. That selectivity is what makes it useful as a research reference compound for GHSR-1a pharmacology in isolation. The molecular weight is approximately 712 daltons.
Because GHRPs and GHRH analogs act through independent receptors, ipamorelin is sometimes studied alongside a GHRH analog like sermorelin or tesamorelin to characterize convergent versus independent contributions to growth-hormone release. That combination research is what generates the recurring question of GHRH-and-GHRP “co-administration” in the literature.
Side-by-side comparison
| **** | Sermorelin | Tesamorelin | Ipamorelin |
|---|---|---|---|
| Class | GHRH analog | GHRH analog (stabilized) | GHRP (selective) |
| Receptor | GHRH-R | GHRH-R | Ghrelin receptor (GHSR-1a) |
| Molecular weight | ~3,358 Da | ~5,135 Da | ~712 Da |
| Half-life | ~10-20 min | ~26 min | ~2 hours (preclinical reports vary) |
| Sequence | GHRH 1-29 | GHRH 1-44 + N-terminal modification | Aib-His-D-2-Nal-D-Phe-Lys-NH2 |
| Selectivity profile | GHRH-R selective | GHRH-R selective | GHSR-1a; minimal cortisol/prolactin/ACTH effect (per Raun 1998) |
| FDA status (US) | Not approved (Geref withdrawn 2008) | Approved (Egrifta / Egrifta SV, HIV lipodystrophy) | Not approved |
Two things this table is not telling you. First, it is a comparison of mechanism and pharmacology, not of clinical effect; clinical efficacy is established only for the one FDA-approved indication for tesamorelin and is not transferable to any other use. Second, the half-life values reported in the literature vary by route, by species, and by assay; the figures above are the ones most commonly cited in published reviews and should be confirmed in any specific source you cite.
Reconstitution math for a 10 mg vial of any of the three
The three peptides differ in molecular weight and somewhat in handling, but the reconstitution math follows the same template. Bacteriostatic water is the standard diluent for multi-access research vials; the 0.9% benzyl alcohol preserves the in-use window.
| Vial mass | BAC water volume | Stock concentration (mg/mL) | Approximate molar concentration (mM) |
|---|---|---|---|
| 10 mg sermorelin | 2.0 mL | 5.0 | ~1.49 |
| 10 mg tesamorelin | 2.0 mL | 5.0 | ~0.97 |
| 10 mg ipamorelin | 2.0 mL | 5.0 | ~7.02 |
| 10 mg of any | 1.0 mL | 10.0 | sermorelin ~2.98 / tesamorelin ~1.95 / ipamorelin ~14.05 |
Note that for the same gravimetric concentration (mg/mL), the molar concentrations differ substantially because ipamorelin is roughly five to seven times smaller than the GHRH analogs. For receptor-binding work, that difference is generally more relevant for receptor pharmacology experiments.
“The pharmacology only translates if the material does. Mass spec for identity, HPLC for purity, Karl Fischer for water content, LAL for endotoxin. On tesamorelin in particular, the chemistry is more structurally complex than sermorelin because of the N-terminal modification, and a clean COA from a reputable third-party lab helps confirm the expected molecular identity.”
Clark Jones, PhD, Velora Research
Working with verified material
Velora supplies all three peptides as research-grade material with batch-specific third-party Certificates of Analysis. The Tesamorelin 10 mg vial is the one most often used in body-composition research, and its COA covers identity by mass spec, purity by HPLC at ≥99%, water content by Karl Fischer, and endotoxin by LAL. The same release protocol applies across the research peptide catalog, and the quality and testing process is documented end to end.
For research designs that compare a GHRH analog to a GHRP at matched receptor exposure, having all three peptides from a single vendor with consistent batch documentation improves reproducibility and documentation across comparative studies.
Frequently asked questions
Is tesamorelin the same thing as Egrifta?
The molecule is the same. The product context is not. Egrifta and Egrifta SV are the FDA-approved drug formulations manufactured for prescription use in HIV-associated lipodystrophy. The tesamorelin Velora sells is research-grade material supplied for in-vitro work and is not the approved drug.
Is sermorelin FDA-approved in the United States?
Not currently. The approved formulation Geref was discontinued from the U.S. market in 2008. Sermorelin is not an approved drug in the United States today.
Is ipamorelin FDA-approved?
No. Ipamorelin is not approved by the FDA or any other national regulator for any indication. It is supplied as a research compound only.
What makes ipamorelin “selective” among GHRPs?
Compared with earlier-generation GHRPs like GHRP-6, ipamorelin’s reported pharmacology shows substantially less effect on cortisol, prolactin, and ACTH release at doses that produce growth-hormone release, per the original characterization by Raun and colleagues in 1998. That selectivity is what makes it useful as a research reference compound for ghrelin-receptor pharmacology in isolation.
Why are GHRH analogs and GHRPs studied together?
Because they act through independent receptors that converge on the same pituitary somatotrophs. Combining them in a research design lets investigators ask whether the two pathways contribute additively or synergistically to growth-hormone release.
Which one shows up in body-composition research?
Tesamorelin, most commonly, because of its FDA-approved indication for visceral fat reduction in HIV lipodystrophy. The Egrifta clinical literature is the largest body of human data on any of these three compounds for body-composition endpoints. That literature applies to the approved indication and population, and it should not be extrapolated to other research framings without explicit study evidence.
Sources and further reading
- Falutz J, Allas S, Blot K, et al. Metabolic Effects of a Growth Hormone–Releasing Factor in Patients with HIV. NEJM. 2007. Full text
- Raun K, Hansen BS, Johansen NL, et al. Ipamorelin, the first selective growth hormone secretagogue. European Journal of Endocrinology. 1998. Full text Full Text
- Stanley TL, Feldpausch MN, Oh J, Branch KL, Lee H, Torriani M, Grinspoon SK Effects of tesamorelin on visceral fat and liver fat in HIV-infected patients with abdominal fat accumulation: a randomized clinical trial. JAMA. 2014. Abstract
- U.S. FDA. Egrifta (tesamorelin for injection) Prescribing Information. FDA label database
This article is provided for laboratory and scientific reference. Tesamorelin is FDA-approved as Egrifta for HIV-associated lipodystrophy; that approved product is a prescription drug and is not the research-grade material Velora supplies. Sermorelin and ipamorelin are not FDA-approved for any indication. Products sold by Velora Research are for in-vitro research use only and are not intended for human or veterinary use. Researchers are responsible for compliance with applicable laws and institutional protocols.
