For Research Use Only. Not for human consumption. The following summarizes published preclinical literature for laboratory research purposes only.
What It Is
Ipamorelin is a synthetic pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2) classified as a growth hormone secretagogue (GHS) and ghrelin-receptor (GHS-R1a) agonist. It belongs to the growth hormone-releasing peptide (GHRP) family but was specifically engineered for receptor selectivity. It was first characterized pharmacologically in the late 1990s as “the first selective growth hormone secretagogue” (Raun et al., Eur J Endocrinol, 1998).
Summary of Published Research Findings
The characterizing study, published in the European Journal of Endocrinology (1998), evaluated ipamorelin in conscious swine, reporting a GH-releasing potency (ED50 = 2.3 ± 0.03 nmol/kg) comparable to GHRP-6. Critically, the same study found that unlike other GHRP-family secretagogues, ipamorelin did not significantly elevate ACTH, cortisol, prolactin, FSH, or LH — even at doses 200-fold above its GH-releasing ED50 — establishing its pharmacological selectivity for the GH axis (Raun et al., 1998).
Because ipamorelin acts on the ghrelin receptor, which is also expressed in the enteric nervous system, a separate line of preclinical research investigated its effects on gastrointestinal motility. In a rat model of surgically induced postoperative ileus, intravenous ipamorelin significantly accelerated gastric emptying and increased cumulative fecal pellet output and food intake compared to vehicle controls (Venkova et al., J Pharmacol Exp Ther, 2009). A follow-up rodent study confirmed ipamorelin reversed surgery-induced delays in gastric emptying through a ghrelin-receptor-mediated, cholinergic-neuron pathway (J Exp Pharmacol, 2012).
These preclinical gut-motility findings informed a Phase 2, multicenter, randomized, double-blind, placebo-controlled human trial (NCT00672074) in 114 post-bowel-resection patients, which found intravenous ipamorelin was well tolerated but did not reach statistical significance for its primary endpoint (time to tolerance of a solid meal: 25.3 h vs. 32.6 h for placebo, p = 0.15) (Int J Colorectal Dis, 2015). This trial is referenced here strictly as research history, not as evidence of therapeutic application.
Proposed Mechanism of Action
The literature proposes that ipamorelin selectively activates the ghrelin receptor (GHS-R1a) on pituitary somatotrophs, triggering GH release through a signaling pathway distinct from the GHRH receptor pathway, while largely sparing off-target activation of the hypothalamic-pituitary-adrenal (HPA) axis. This selectivity is attributed to its specific peptide backbone conformation, which differentiates it from earlier, less-selective GHRP compounds such as GHRP-6.
Research Use Only / Handling Note
Ipamorelin acetate for laboratory use is supplied as a lyophilized powder. Strictly for laboratory research; not for human or veterinary use.