Ipamorelin

Molecular Information

Research Summary

Ipamorelin is considered one of the most selective GH secretagogues studied, primarily activating the ghrelin/GHS receptor to stimulate growth hormone release from the anterior pituitary. Unlike earlier GH secretagogues such as GHRP-6 and GHRP-2, ipamorelin demonstrates high selectivity for GH release without significantly affecting ACTH, cortisol, or prolactin levels in animal models. This selectivity has made it particularly valuable in research settings where isolated GH pathway modulation is desired.

Mechanism of Action

Ipamorelin acts as a selective agonist at the growth hormone secretagogue receptor (GHS-R1a), the endogenous receptor for ghrelin. Receptor activation triggers calcium influx through voltage-gated calcium channels, leading to GH vesicle release. Unlike less selective GHS-R agonists, ipamorelin does not significantly activate ACTH or cortisol release pathways, suggesting receptor subtype selectivity or differential signaling.

Published Animal Studies

• [1]Rat studies demonstrated dose-dependent GH release with minimal effects on ACTH, cortisol, and prolactin (Raun et al., 1998)
• [2]Swine models confirmed GH secretagogue activity with favorable selectivity profile (Johansen et al., 1999)
• [3]Chronic administration studies in rats showed maintained GH response without significant tachyphylaxis
• [4]Combination studies with CJC-1295 in animal models demonstrated synergistic GH release (Veldhuis et al., 2005)

In-Vitro Research

• •GHS-R1a receptor binding assays demonstrated high-affinity selective agonism
• •Pituitary cell cultures showed GH release without significant PRL or ACTH co-secretion
• •Comparison studies with GHRP-6 demonstrated superior selectivity in cell-based assays

Research Applications

References

1. 1.Raun K, et al. "Ipamorelin, the first selective growth hormone secretagogue." Eur J Endocrinol. 1998;139(5):552-561.
2. 2.Johansen PB, et al. "Pharmacokinetics of ipamorelin." Eur J Pharm Sci. 1999;7(4):311-316.