Ipamorelin
First described by Raun and colleagues at Novo Nordisk (1998) as 'the first selective growth hormone secretagogue' because it releases GH without meaningfully raising ACTH, cortisol or prolactin. Human evidence is confined to phase 1/2 studies and there is no approved therapeutic indication.
Mechanism
In plain terms it acts like the hunger hormone ghrelin to switch on growth-hormone release. Technically it is an agonist at the growth hormone secretagogue receptor GHS-R1a (the ghrelin receptor) on pituitary somatotrophs; receptor activation couples through Gq/11 and phospholipase C to generate IP3, releasing intracellular calcium and driving exocytosis of stored growth hormone. Its relative selectivity for GH over ACTH, cortisol and prolactin distinguishes it from earlier secretagogues (Raun et al., 1998).
Regulatory Status by Region
- United States (FDA)Not approved for any indication. FDA removed ipamorelin acetate from Category 2 of the interim 503A bulks list (September 2024) after the nomination was withdrawn and did not add it to the compoundable 503A list; PCAC review did not support inclusion.
- Australia (TGA)Not on the ARTG; an unapproved growth hormone secretagogue. Supply for human therapeutic use is restricted (prescription-only class) with no approved indication.
- European Union (EMA)No EMA marketing authorization; not an approved medicine in the EU.
- WADAProhibited at all times under Section S2; growth hormone secretagogues including ipamorelin are explicitly listed.
Key Studies
- Ipamorelin, the first selective growth hormone secretagogue (Raun K, Hansen BS, Johansen NL, et al. Eur J Endocrinol. 1998;139(5):552-561. PMID 9849822)
- Prospective, randomized, controlled, proof-of-concept study of the ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients (Beck DE, et al. Int J Colorectal Dis. 2014;29(12):1527-1534 (phase 2 RCT, n=114; NCT00672074; negative primary endpoint))