Ipamorelin — Published Research

In swine pituitary cell cultures, ipamorelin stimulated GH release with an EC₅₀ of approximately 1.3 nM. At effective concentrations, the peptide did not alter ACTH, cortisol, prolactin, FSH, or LH levels in vivo. This selectivity profile was confirmed in both rat and dog models. Comparison studies showed that GHRP-6 and GHRP-2 at comparable concentrations produced significant increases in cortisol and prolactin, while ipamorelin did not, establishing it as the first truly selective GHS. Research compound — not for human use.

Raun K et al. “Ipamorelin, the first selective growth hormone secretagogue.” Eur J Endocrinol. 1998. PubMed

Ipamorelin activates the GHS-R1a receptor, a seven-transmembrane G protein-coupled receptor. Upon ligand binding, GHS-R1a couples primarily to Gαq/11, activating phospholipase C and generating IP3 and DAG second messengers. This leads to calcium release from intracellular stores and protein kinase C activation, triggering GH vesicle exocytosis from somatotrophs. The GHS-R1a receptor also exhibits constitutive (ligand-independent) activity of approximately 50% of maximal signaling, which is unique among peptide hormone receptors. Research compound — not for human use.

Howard AD et al. “A receptor in pituitary and hypothalamus that functions in growth hormone release.” Science. 1996. PubMed

GHS-R1a receptors are expressed on enteric neurons in addition to pituitary somatotrophs. In rodent models, ipamorelin modulated gastrointestinal motility patterns through GHS-R1a activation on myenteric plexus neurons, influencing cholinergic signaling pathways. These preclinical studies characterize the enteric receptor distribution and downstream signaling mechanisms of growth hormone secretagogues in the GI tract. Research compound — not for human use.

Greenwood-Van Meerveld B et al. “Ipamorelin, a ghrelin mimetic, modulates gastric motility in rodents.” Eur J Pharmacol. 2007. PubMed