Ipamorelin

Ipamorelin is a synthetic pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2) first described by Raun and colleagues in 1998 as the first highly selective growth hormone (GH) secretagogue. It belongs to the growth-hormone-releasing peptide (GHRP) class and acts as an agonist at the growth hormone secretagogue receptor type 1a (GHS-R1a), the ghrelin receptor, on pituitary somatotrophs. Its main distinguishing feature is selectivity: in preclinical work it triggered GH release without the clinically meaningful rises in cortisol, ACTH, or prolactin seen with earlier GHRPs such as GHRP-6, and without the appetite stimulation associated with ghrelin agonism in some models. This made it attractive as a research tool for studying GH biology. Ipamorelin was originally developed by Novo Nordisk and later studied (by Helsinn) for postoperative ileus. It reached Phase 2 human trials but was not approved for any indication and development was discontinued. Today it is sold only as a research chemical and is widely discussed in fitness and longevity communities, frequently stacked with the GHRH analog CJC-1295. It is not approved by the FDA for human use. Claims around body composition, recovery, and anti-aging are largely extrapolated from GH physiology and animal data rather than confirmed by robust human outcome trials.