Ipamorelin — Canada Research Brief

Mechanism and selectivity

Ipamorelin is a pentapeptide designed at Novo Nordisk by screening derivatives of GHRP-1 for selective GH release. The key finding — reported by Raun et al. (European Journal of Endocrinology 1998) — was that ipamorelin stimulated GH release in rats and pigs at potencies equivalent to GHRP-2 and GHRP-6 but, uniquely, did not produce significant elevations in ACTH, cortisol, or prolactin.

That selectivity is the defining feature of ipamorelin in the literature. The structural reason is that its D-2-Nal and D-Phe substitutions favour binding to the ghrelin/GHS-R1a receptor without activating the secondary receptors responsible for the ACTH/cortisol arm of earlier GHRPs.

Research pairing with CJC-1295

Ipamorelin is most commonly studied in combination with a GHRH analogue (sermorelin, modified GRF 1-29, or CJC-1295) because the two receptors converge on the same somatotroph. The combined GH pulse is larger than either alone — see our CJC-1295 vs ipamorelin comparison for the mechanistic breakdown.

Storage

Store lyophilised ipamorelin at −20°C protected from light. Reconstituted peptide is stable refrigerated at 2–8°C for 2–4 weeks. Avoid repeated freeze-thaw cycles.