Ipamorelin and hexarelin are both GHRPs that act on the ghrelin receptor (GHS-R1a) — but they sit at opposite ends of a selectivity-versus-potency trade-off.
Research reference only. Not medical advice, prescribing guidance, or a product recommendation.
| Dimension | Ipamorelin | Hexarelin |
|---|---|---|
| Class | Pentapeptide GHRP | Hexapeptide GHRP (GHRP-6 analog) |
| Receptor | GHS-R1a (ghrelin receptor) | GHS-R1a + CD36 |
| GH potency | Moderate, selective | High — strongest of common GHRPs |
| Cortisol / ACTH | Minimal (selective) | Can elevate |
| Prolactin | Minimal | Can elevate |
| Receptor desensitization | Lower | Greater |
| Notable extra activity | — | CD36-mediated cardioprotection (preclinical) |
| FDA approval | None | None |
| Characterizing study | Raun et al., 1998 | GHRP-6 analog literature |
Ipamorelin was characterized as the first GHRP to release GH without meaningfully raising ACTH, cortisol, or prolactin (Raun et al., 1998, Eur J Endocrinol) — a “clean” selective profile that also shows less receptor desensitization over repeated exposure. That selectivity is its defining research feature.
Hexarelin releases more GH per dose than GHRP-2, GHRP-6, or ipamorelin, making it the more potent secretagogue — but it recruits cortisol and prolactin and desensitizes the receptor faster. It also carries a distinct research thread: CD36-mediated cardioprotective effects independent of GH release.
If the research question prioritizes a clean, sustainable GH signal, ipamorelin’s selectivity is the draw. If it prioritizes raw GH output (or the separate CD36 / cardiac line of inquiry), hexarelin is the more potent but less selective tool. Both act on the same receptor, both are commonly studied with a GHRH analog, and neither is FDA-approved.
Both are GHRPs acting on the ghrelin receptor (GHS-R1a). Ipamorelin is selective, releasing GH without meaningfully raising cortisol or prolactin. Hexarelin is more potent but also elevates cortisol and prolactin and desensitizes the receptor faster.
In its characterizing study (Raun et al., 1998), ipamorelin released GH without the ACTH and cortisol increases seen with earlier GHRPs, earning it the description “the first selective growth hormone secretagogue.”
Beyond GH release, hexarelin binds the CD36 receptor, through which preclinical studies report cardioprotective effects independent of growth hormone.
No. Both are research compounds and are not FDA-approved; both are also prohibited in sport. This page is a research and educational reference.