Ipamorelin

Ipamorelin is a synthetic pentapeptide that acts as a selective growth hormone secretagogue (GHS). It works by binding to the ghrelin receptor (also known as GHS-R1a) on pituitary cells, triggering a short, pulsatile release of growth hormone (GH). Ipamorelin is noted for its selectivity — unlike some other growth hormone releasing peptides, it does not significantly stimulate the release of cortisol, prolactin, or aldosterone, which are considered undesirable side effects in the context of GH modulation.

Ipamorelin has been studied in early-phase clinical research and pharmacokinetic modeling, but it has not advanced through full clinical development and is not FDA-approved for any human use. It remains one of the most discussed research peptides in the growth hormone secretagogue category.

Published clinical pharmacology data on ipamorelin include Phase 1 and pharmacokinetic/pharmacodynamic (PK/PD) studies in healthy adults. A 1999 PK/PD modeling study characterized ipamorelin's GH response as a short, dose-dependent pulse with a terminal half-life of approximately two hours after intravenous administration. Additional research explored its effects on postoperative bowel function, where it showed some promise as a prokinetic agent but did not advance to approval.

Ipamorelin is frequently discussed in combination with CJC-1295, based on the rationale that combining a GHRH analog with a ghrelin receptor agonist could produce complementary effects on GH release. However, well-controlled human trials evaluating this combination for body composition or performance outcomes have not been published.