Ipamorelin Acetate

Ipamorelin is a synthetic pentapeptide growth hormone secretagogue (GHS) composed of five non-standard amino acids: Aib-His-D-2Nal-D-Phe-Lys-NH2, where Aib is α-aminoisobutyric acid and D-2Nal is D-2-naphthylalanine. Developed from structure-activity relationship studies on GHRP-1, ipamorelin was designed to maximize selectivity for the ghrelin/growth hormone secretagogue receptor (GHSR-1a) while minimizing stimulation of other pituitary hormones. It functions as a full agonist at GHSR-1a, the same receptor engaged by endogenous ghrelin, triggering rapid GH release from pituitary somatotroph cells with peak serum GH concentrations approximately 40 minutes post-administration. The defining pharmacological feature of ipamorelin is its remarkable receptor selectivity. Unlike other GHSPs (GHRP-2, GHRP-6), ipamorelin does not significantly elevate ACTH, cortisol, prolactin, or FSH even at doses exceeding 200-fold the ED50 for GH release. This selectivity closely resembles the hormonal profile of endogenous GHRH stimulation, making ipamorelin pharmacologically "clean" and valuable for isolating GH-specific effects in research without confounding adrenocortical or prolactin-mediated phenomena. Research applications include growth hormone axis physiology, body composition studies (lean mass vs. fat mass), gastroenterology (postoperative ileus and gut motility via ghrelin receptor pathways), and neuroscience investigations of GHSR-1a in hippocampal synaptic plasticity, memory consolidation, and dendritic spine formation. The peptide's high selectivity and well-characterized pharmacology have established it as a key tool for mechanistic GH research.