Ipamorelin, the first selective growth hormone secretagogue, stimulates growth hormone secretion without affecting prolactin, ACTH, or cortisol[1]
This landmark pharmacological study characterized ipamorelin as a novel, highly selective GH secretagogue in rats and swine. In concentration-response studies, ipamorelin stimulated concentration-dependent GH release with an ED50 in the picomolar range at the pituitary level. In contrast to GHRP-6 and GHRP-2, ipamorelin did not significantly elevate cortisol, ACTH, aldosterone, or prolactin at any GH-releasing concentration tested. The selectivity was attributed to ipamorelin's binding profile at GHS-R subtypes -- functional activity was concentrated at the GHSR-1a receptor subtype responsible for somatotroph GH release.
Last verified: 2026-04-03
Effects of ipamorelin alone and in combination with a GHRH analog on growth hormone secretion and bone density in rodent models[2]
This study evaluated ipamorelin's effects on GH pulsatility and bone mineral density in aged, GH-deficient rats over 12 weeks of subcutaneous administration. Ipamorelin significantly increased GH pulse amplitude and mean 24-hour GH concentrations without affecting pulse frequency, a pattern consistent with physiologic GH secretion. Dual-energy X-ray absorptiometry demonstrated significantly increased bone mineral density in the femur and tibia of ipamorelin-evaluated animals compared to vehicle controls. When combined with a GHRH analog, synergistic GH release was observed, supporting the utility of combined secretagogue protocols in research settings.
Last verified: 2026-04-03
