Ipamorelin

What is Ipamorelin?

Ipamorelin is a synthetic pentapeptide developed in the late 1990s as a selective growth-hormone-releasing peptide (GHRP). It contains non-natural residues (Aib, D-2-Nal, D-Phe) that confer protease resistance. Among the GHRPs, Ipamorelin is one of the most selective for growth hormone release with minimal effects on prolactin, ACTH, or cortisol in published preclinical and early clinical studies.

Mechanism of action (preclinical evidence)

Ipamorelin is a selective agonist of the growth hormone secretagogue receptor type 1a (GHSR1a), the canonical ghrelin receptor expressed primarily on somatotrophs in the anterior pituitary. The receptor is Gαq-coupled; activation triggers phospholipase C, IP3-mediated calcium release, and ultimately exocytosis of growth hormone (GH) granules from the somatotrophs. Ipamorelin's distinguishing feature among growth hormone-releasing peptides (GHRPs) is its receptor selectivity. While first-generation GHRPs such as GHRP-6 and GHRP-2 cross-react with receptors that drive prolactin, ACTH, and cortisol release, Ipamorelin shows minimal activation of these off-target pathways at standard preclinical doses. This selectivity has practical research utility: it isolates GHSR1a-driven biology from confounding HPA-axis and prolactin effects. The pulsatile pattern of GH release induced by Ipamorelin appears to preserve the physiological feedback loop with somatostatin and IGF-1, in contrast to chronic exogenous GH administration, which suppresses endogenous secretion. Co-administration with a GHRH analog (such as Sermorelin or CJC-1295 without DAC) produces a synergistic GH release greater than either compound alone, reflecting the complementary mechanisms of GHRH (somatotroph priming) and GHRP (acute secretion). The receptor exhibits rapid desensitization, which is why preclinical protocols typically use intermittent rather than continuous administration. Beyond pituitary effects, GHSR1a is expressed in the hypothalamus and reward circuits, raising questions about appetite and metabolic effects that remain under preclinical investigation.

Research applications

• GHSR1a receptor binding and pharmacology
• Pituitary somatotroph cell function studies
• Ghrelin pathway investigations
• Growth hormone release dynamics in rodent models
• Comparative studies with other GHRPs (GHRP-2, GHRP-6, hexarelin)

Storage and handling

Store lyophilised Ipamorelin at -20 °C, sealed and protected from light. Reconstitute in sterile water for short-term assays; aliquot for freezer storage when not in immediate use.

Regulatory status

Ipamorelin is not approved by FDA, EMA, or any other regulator for human or veterinary use. WADA prohibits all GHRPs (S2 category). Supplied strictly for laboratory research only.

Frequently asked questions