Ipamorelin is a pentapeptide that showed a significant growth hormone secretion potential both in vitro and in vivo studies. In vivo studies, it showed a similar potency and effectiveness as GHRP-6 (a synthetic growth hormone-releasing hexapeptide) as it stimulates GH release via the GHRP receptors.

What’s interesting about ipamorelin is that it did not raise ACTH (Adrenocorticotropic hormone) nor cortisol level significantly; something we’ve seen happening with GHRP-6 and GHRP-2. So, we can conclude that ipamorelin is the first GHRP-receptor agonist with GH release selectivity similar to GHRH. This is why ipamorelin is an interesting candidate for further testing.

In addition to stimulating GH secretion, this peptide has seen some interesting use in the treatment of postoperative ileus (POI), a condition characterized by transient loss of gastrointestinal motility following abdominal surgery.

The exact mechanism behind POI is a complex one, involving many different bodily structures; in addition, condition is often worsen due to the opioid drugs used for patient pain management.

In rodent studies, ipamorelin was found to selectively stimulate ghrelin (hormone produced by our stomach, affecting food intake, deposition and growth hormone release) without raising cortisol or adrenocorticotropic hormone levels. These effects were shown in both lower GI tract as well as the upper, making this peptide a viable candidate for potential POI treatment.

References:

Raun K, Hansen BS, Johansen NL, Thøgersen H, Madsen K, Ankersen M, Andersen PH. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998 Nov;139(5):552-61. doi: 10.1530/eje.0.1390552. PMID: 9849822.

Greenwood-Van Meerveld B, Tyler K, Mohammadi E, Pietra C. Efficacy of ipamorelin, a ghrelin mimetic, on gastric dysmotility in a rodent model of postoperative ileus. J Exp Pharmacol. 2012 Oct 19;4:149-55. doi: 10.2147/JEP.S35396. PMID: 27186127; PMCID: PMC4863553.