Ipamorelin

Ipamorelin is a synthetic pentapeptide developed as a growth hormone secretagogue (GHS) and selective agonist of the ghrelin receptor (GHSR-1a). It was synthesized in the late 1990s by Novo Nordisk (compound NNC 26-0161) as part of a research program to develop GHS compounds with improved selectivity profiles. Unlike earlier secretagogues such as GHRP-6 or GHRP-2, ipamorelin demonstrates highly specific stimulation of GH release with minimal cross-activation of other pituitary axes.

The selectivity of ipamorelin is its defining research characteristic. In preclinical studies using rat pituitary cell cultures and in vivo models, ipamorelin produced robust dose-dependent GH release while showing negligible effects on plasma ACTH, cortisol, or prolactin — hormones that are frequently co-stimulated by less selective GHS compounds. This selectivity makes ipamorelin a valuable pharmacological tool for research designs that require isolated modulation of the GH/IGF-1 axis.

Research with ipamorelin has been conducted across several model systems. Studies in aged animal models have documented the ability of ipamorelin to partially restore GH pulse amplitude that declines with aging. Additional research has examined its effects on bone mineral density in animal models, with findings of increased bone formation markers. Ipamorelin has also been used as a reference compound in receptor pharmacology studies characterizing GHSR-1a binding.

Ipamorelin is available for in vitro and in vivo preclinical research use only and is not approved for human therapeutic application. Researchers designing GH axis studies will find ipamorelin's selectivity profile particularly useful for isolating GH-specific effects from confounding changes in stress-axis hormones.