Ipamorelin: The First Selective Growth Hormone Secretagogue

Ipamorelin is a synthetic pentapeptide, Aib-His-D-2-Nal-D-Phe-Lys-NH2, formula C38H49N9O5, molecular weight 711.9 g/mol. Two of its five residues are non-standard, which is part of what gives it stability. The 1998 founding study by Raun and colleagues reported that it released growth hormone from rat pituitary cells with potency comparable to GHRP-6, acting through a GHRP-like receptor, and did so without raising ACTH or cortisol. That selectivity is where the name “the first selective growth hormone secretagogue” comes from.

The preclinical record spans more than one tissue. A 1999 study in adult female rats reported a dose-dependent increase in longitudinal bone growth rate at the proximal tibia over 15 days, from 42 µm/day in controls to 52 µm/day at the highest dose, with no change in total IGF-I. A separate line of work looked at the gut: a 2012 study in a rodent model of postoperative ileus reported that ipamorelin accelerated gastric emptying through a GHS-receptor-mediated cholinergic mechanism.

Ipamorelin was assigned the development code NNC 26-0161. It holds no approved human indication in any major jurisdiction, and the published record is predominantly preclinical.

Supplied for laboratory research use only.