Comparison
Ipamorelin vs Sermorelin
Ipamorelin and Sermorelin both stimulate growth hormone release but act on different receptors: Ipamorelin is a selective GHSR-1a (ghrelin receptor) agonist, while Sermorelin is a GHRH receptor agonist. They are frequently studied on separate, complementary pathways.
Ipamorelin and Sermorelin both increase growth hormone (GH) release, but they act on two entirely separate receptor systems, which is the central distinction researchers study. Ipamorelin is a selective pentapeptide ghrelin mimetic (molecular weight 711.9 Da, half-life ~2 hours) that binds the growth hormone secretagogue receptor type 1a (GHSR-1a). Sermorelin is a 44-amino-acid analog of growth hormone-releasing hormone (molecular weight 3,357.9 Da, half-life ~10–20 minutes) that binds the GHRH receptor (GHRHR).
How do Ipamorelin and Sermorelin differ?
Research shows Ipamorelin activates GHSR-1a, triggering Gq/11 signalling and intracellular calcium rise to drive GH exocytosis, while producing minimal cortisol, prolactin, or ACTH elevation — the selectivity profile documented by Raun et al. (1998, PMID: 9241518). Sermorelin activates GHRHR, raising intracellular cAMP via adenylate cyclase to stimulate GH synthesis and pulsatile release, and it preserves the physiological feedback loop so elevated IGF-1 suppresses further release (Khorram et al., 1997, PMID: 9275068).
Why are they studied together?
Because the two peptides act on independent receptors, researchers commonly study a GHRH analog paired with a GHSR-1a agonist for synergistic GH pulse amplification. In that context, Sermorelin (or CJC-1295) supplies the GHRH-pathway signal and Ipamorelin supplies the ghrelin-pathway signal.
| Metric | Ipamorelin | Sermorelin |
|---|---|---|
| Class | Selective GH secretagogue (ghrelin mimetic) | GHRH analog (GHRH 1–44) |
| Receptor target | GHSR-1a (ghrelin receptor) | GHRHR (GHRH receptor) |
| Sequence length | 5 amino acids | 44 amino acids |
| Molecular weight | 711.9 Da | 3,357.9 Da |
| Half-life | ~2 hours | ~10–20 minutes |
| Signalling | Gq/11 → Ca²⁺ → GH exocytosis | cAMP → GH synthesis/release |
| Off-target hormones | Minimal cortisol/ACTH/prolactin | Minimal; feedback loop preserved |
| Key reference | PMID: 9241518 | PMID: 9275068 |
See the Ipamorelin monograph and the Sermorelin monograph for full citation summaries.
Research Use Only · Not for human consumption · Not for veterinary use.