IpamorelinSelective GH Secretagogue & GHSR-1a Agonist — Research Reference by QSC Peptides

Ipamorelin (NNC 26-0161, Aib-His-D-2-Nal-D-Phe-Lys-NH₂) is a synthetic pentapeptide that acts as a selective agonist at the growth hormone secretagogue receptor 1a (GHSR-1a), also called the ghrelin receptor. GHSR-1a is a Gq-protein-coupled receptor expressed on pituitary somatotrophs and hypothalamic neurons.

Receptor activation stimulates phospholipase C → IP3 → intracellular Ca²⁺ release → GH granule exocytosis. GHSR-1a activation on hypothalamic interneurons also suppresses somatostatin tone, amplifying GH pulse amplitude at the pituitary.

Why Ipamorelin Is Uniquely Selective

The defining characteristic of Ipamorelin is its exceptional receptor selectivity. Its D-2-Nal (D-2-naphthylalanine) and D-Phe residues optimize hydrophobic GHSR-1a binding contacts while avoiding the secondary receptor interactions that cause cortisol and prolactin elevation in GHRP-2 and GHRP-6. At all tested research concentrations, Ipamorelin produces no measurable ACTH, cortisol, or prolactin elevation — making it the cleanest GH-stimulating tool available from QSC Peptides.

Synergy with GHRH Analogs

Ipamorelin acts on GHSR-1a (ghrelin receptor); GHRH analogs (CJC-1295, Sermorelin) act on GHRHR. These two receptor systems are fully complementary — co-stimulation produces additive to synergistic GH pulse amplification. This is the mechanism behind the QSC Peptides CJC-1295 + Ipamorelin GH Stack blend.