Ipamorelin — Selective GHRP

Background

Ipamorelin is a synthetic pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH₂) developed by Novo Nordisk in the late 1990s as a selective growth hormone secretagogue acting at the ghrelin receptor (GHS-R1a).

Mechanism

Ipamorelin selectively activates the ghrelin receptor on pituitary somatotrophs, producing a brief pulse of growth hormone release without significant activation of ACTH, cortisol, prolactin, FSH, LH, or TSH pathways — distinguishing it from earlier GHRPs (GHRP-2, GHRP-6) which show off-target endocrine effects.

What is proven

Early-phase human pharmacokinetic and pharmacodynamic studies confirm selective GH release with negligible effect on ACTH, cortisol, and prolactin at tested doses. IGF-1 elevation is dose-dependent.

Animal work shows lean-mass preservation and bone-mineral effects consistent with physiological GH/IGF-1 axis activation.

What is NOT proven

No completed Phase 3 trials establishing efficacy and long-term safety in humans for any indication. Novo Nordisk discontinued development of ipamorelin for postoperative ileus in 2007 after Phase 2 efficacy did not meet endpoints in that specific indication.

Body-composition and anti-ageing claims rest on pharmacology, not on registrational outcome trials.

Open research questions

Optimal dosing schedule (pulsatile vs continuous), combination effects with GHRH analogues (CJC-1295), long-term IGF-1 elevation safety profile.

Regulatory status

Not approved by any major regulator.

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