Ipamorelin

The first selective growth-hormone secretagogue — it triggers a clean GH pulse through the ghrelin receptor without raising cortisol, ACTH, or prolactin.

01Overview

Ipamorelin is a synthetic pentapeptide in the growth-hormone-secretagogue (GHS) class, first characterized by Raun and colleagues in 1998 and developed at Novo Nordisk. Its incorporation of non-natural amino acids (such as Aib and D-2-naphthylalanine) makes it resistant to enzymatic breakdown.

It is prized in research as the benchmark for selectivity: it stimulates GH without the off-target hormonal effects that limit earlier GHRPs.

02Mechanism

• Acts as a selective agonist at the ghrelin / growth-hormone-secretagogue receptor (GHS-R1a) on pituitary somatotrophs.
• Receptor binding activates Gq/11-linked phospholipase C, generating IP3 and mobilizing intracellular calcium to drive GH-granule release.
• Unlike GHRP-6 or hexarelin, it does not meaningfully raise cortisol, ACTH, prolactin, or appetite.

03Research uses

• Selective GH-secretagogue research
• Ghrelin-receptor (GHS-R1a) pharmacology
• GH-axis and IGF-1 dynamics without endocrine confounders

04Key findings

• The 1998 characterization showed GH release comparable to GHRP-6 with no significant elevation of ACTH, cortisol, or prolactin.
• PK modeling in human volunteers reported a short half-life of roughly two hours.
• Its clean profile makes it a common standard for benchmarking new secretagogues and isolating GH-dependent effects.

05Handling & reconstitution

• Supplied as a white lyophilized powder; stable in freeze-dried form.
• Reconstitute with bacteriostatic water using sterile technique; swirl gently.
• Store reconstituted solution refrigerated and protected from light.