GHS-R

GHS-R, also called the ghrelin receptor, is a G-protein-coupled receptor expressed primarily in the pituitary and hypothalamus. Activating GHS-R triggers growth hormone release and ghrelin-mediated effects on appetite, gastric motility, and reward signaling.

GHRPs (Growth Hormone-Releasing Peptides) such as ipamorelin, GHRP-2, GHRP-6, and hexarelin all act as GHS-R agonists. Of these, ipamorelin is considered the most selective — it stimulates GH release without significantly activating the cortisol or prolactin pathways that less-selective GHRPs are known to elevate. MK-677 (ibutamoren), an orally active small molecule, is also a GHS-R agonist with a half-life long enough to support once-daily dosing.

Receptor desensitization is a real concern with GHS-R agonists: chronic high-dose stimulation down-regulates the receptor, which is why most research protocols cycle these compounds rather than running them continuously.