IpamorelinGrowth Hormone

Overview

Ipamorelin is a synthetic pentapeptide growth-hormone secretagogue, first characterized in 1998 as the "first selective" GH secretagogue. It acts as a ghrelin-receptor (GHS-R1a) agonist, stimulating pulsatile GH release from the pituitary while, in animal studies, having little effect on ACTH, cortisol or prolactin. It was later developed as an injectable drug candidate for postoperative ileus but was never approved for any indication. It remains a research-use-only compound.

Mechanism

Ipamorelin binds and activates the growth-hormone secretagogue receptor type 1a (GHS-R1a), the same Gq-coupled GPCR targeted by endogenous ghrelin, driving a PLC/IP3 calcium-mobilization pathway in pituitary somatotrophs that triggers GH secretion. In the original animal characterization it matched GHRP-6's GH-releasing potency yet, unlike other secretagogues, did not significantly raise ACTH or cortisol — a comparatively selective profile. That selectivity claim derives from rat/swine and in-vitro data, not controlled human endocrine studies.

Clinical evidence

Foundational evidence is preclinical: the 1998 characterization was in rats and swine, and a 2009 study showed repetitive IV ipamorelin improved gastrointestinal transit and food intake in a rodent postoperative-ileus model. Human data are limited to an early-phase program: a phase 2, randomized, double-blind, placebo-controlled trial (Helsinn; NCT00672074) tested IV ipamorelin for postoperative ileus in bowel-resection patients. The drug was well tolerated but did not significantly outperform placebo on its primary endpoint (time to first tolerated meal) or secondary endpoints, and the program did not advance to approval. There are no controlled human trials supporting body-composition, anti-aging or performance uses.

Safety profile

Ipamorelin is not FDA-approved for any use, and long-term human safety has not been established. The strongest human signal is reassuring but narrow: short-term IV dosing (up to ~7 days) in the phase 2 ileus trial was well tolerated, with adverse events similar to placebo. As a GH secretagogue it can be expected to raise GH/IGF-1 and may affect glucose metabolism, so effects with sustained use are plausible but unstudied. Research use only; there is no validated human dosing and nothing here is therapeutic guidance.

Compare

• vs CJC-1295 (No-DAC)

  Short-acting GHRH analog commonly stacked with this GHRP for a synergistic pulse.

• vs CJC-1295 DAC

  Long-acting GHRH analog; the other half of a common GHRP + GHRH pairing.

• vs Sermorelin

  A GHRH-receptor agonist (different class); GHRP vs GHRH comparison.