Ipamorelin

Ipamorelin is a synthetic pentapeptide (5 amino acids) that selectively binds the Growth Hormone Secretagogue Receptor 1a (GHSR-1a) — also known as the ghrelin receptor — on anterior pituitary somatotrophs. This triggers dose-dependent growth hormone release. It was developed by Novo Nordisk and described by Raun et al. (1998) as the first pentapeptide GH secretagogue with a clean selectivity profile: effective GH release with no cortisol, ACTH, or prolactin elevation.

All three are GHSR-1a agonists that stimulate GH release. The key distinction is selectivity: GHRP-6 and GHRP-2 significantly elevate cortisol, ACTH, and prolactin alongside GH. Ipamorelin does not — even at doses producing maximum GH stimulation. This makes ipamorelin a cleaner research tool for studying isolated GH secretion without confounding stress-hormone activation. GHRP-6 also strongly stimulates appetite via hypothalamic pathways; ipamorelin's appetite effect is minimal.

Preclinical research (Raun et al. 1998) demonstrated dose-dependent GH release (ED50 ~80 nmol/kg), no cortisol or prolactin elevation, and a 24% increase in bone growth rate (52 vs 42 µm/day) in rat models. Human pharmacokinetic data (Frieboes et al. 2004) confirmed GH elevation during nocturnal sleep phases with a ~2-hour half-life and peak GH response at approximately 40 minutes. All preclinical findings should not be extrapolated to human use.

Ipamorelin (GHSR-1a agonist) and CJC-1295 (GHRH-R agonist) work through complementary and synergistic receptor pathways. GHRH and GH secretagogues act at different pituitary receptor sites and their combination produces additive or supra-additive GH pulse amplitude responses. Research protocols studying this combination aim to maximize GH pulse magnitude while preserving pulsatility — an area of active preclinical investigation.

No. Ipamorelin is not FDA-approved for any indication. It is classified as a research compound and is sold exclusively for in vitro research purposes. No Phase 3 clinical trials have been completed. Some compounding pharmacies have included it in formulations, which the FDA has flagged. It is not intended for human therapeutic use.

Lyophilized ipamorelin should be stored at -20°C for long-term stability (up to 24 months). Once reconstituted with bacteriostatic water, store at 2–8°C and use within 30 days. Avoid repeated freeze-thaw cycles. The pentapeptide structure is relatively stable in lyophilized form but degrades more rapidly once in solution.