Ipamorelin

Ipamorelin is a synthetic pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2, derived from GHRP-1) that acts as a selective agonist of the growth hormone secretagogue receptor type 1a (GHS-R1a), the ghrelin receptor expressed in the anterior pituitary and hypothalamus. Receptor activation drives Gq/11-phospholipase C/IP3 signaling and intracellular calcium release, stimulating pulsatile growth hormone (GH) secretion, which in turn raises hepatic IGF-1. It is described as the first selective GH secretagogue, releasing GH without significantly elevating ACTH, cortisol, prolactin, FSH, LH, or TSH.

Human evidence

Some human data (Phase 2 trials completed but unsuccessful); not approved for any indication

Regulatory status

Not approved by the FDA (or any major regulator) for any indication. Originally developed by Novo Nordisk and later studied by Helsinn Therapeutics for postoperative ileus, where Phase 2 development was discontinued for lack of efficacy. Ipamorelin acetate was removed from Category 2 of the FDA's interim 503A bulk drug substances list in September 2024 (effective September 27, 2024, after its nomination was withdrawn) and referred to the Pharmacy Compounding Advisory Committee (PCAC); at the October 29, 2024 PCAC meeting the committee voted against adding ipamorelin to the 503A bulks list. It is NOT among the peptides on the FDA's July 23-24, 2026 PCAC agenda (announced in an April 16, 2026 Federal Register notice, Docket FDA-2025-N-6895), which covers BPC-157, KPV, TB-500, MOTS-c, DSIP, Semax, and Epitalon. Marketed only as a research-use chemical, not as an approved medicine.

• —Studied as a tool for stimulating endogenous, pulsatile growth hormone and IGF-1 release in pharmacology and endocrinology research.
• —Investigated clinically for accelerating recovery of bowel function (postoperative ileus) after abdominal surgery; Phase 2 development was discontinued for lack of efficacy.
• —Explored in the broader research context of growth hormone deficiency and conditions involving muscle wasting/cachexia as a GH secretagogue.
• —Used in receptor-pharmacology research as a reference selective GHS-R1a agonist to study GH release independent of ACTH, cortisol, and prolactin pathways.

• ⚠Not an approved drug: it has no established human dosing, manufacturing, or safety standards, and research-grade ('not for human use') material has unverified purity and content.
• ⚠In completed human trials it was generally reported as well tolerated with no serious adverse events attributed to it; the most commonly noted mild effects in GH-secretagogue research are transient nausea, headache, and lightheadedness, with the broader class also associated with water retention, joint discomfort, and changes in insulin sensitivity/blood glucose.
• ⚠At the October 2024 PCAC review, committee members cited concerns over class-associated adverse effects such as fluid retention, congestive heart failure, and hyperglycemia, and a lack of evidence supporting clinical efficacy and safety.
• ⚠Reported elimination half-life is roughly 2 hours.
• ⚠Prohibited in sport at all times by the World Anti-Doping Agency under class S2 (peptide hormones, growth factors and related substances) and detectable in anti-doping testing.