GHSR

Definition

The Growth Hormone Secretagogue Receptor (GHSR), also known as the ghrelin receptor, is a G protein-coupled receptor (GPCR) primarily expressed in the hypothalamus and pituitary gland. It plays a central role in growth hormone release, appetite regulation, and energy homeostasis.

GHSR Subtypes and Signalling

GHSR exists in two forms: GHSR-1a (the active, signalling form) and GHSR-1b (a truncated variant with no known signalling function but potential modulatory role). GHSR-1a signals primarily through Gαq/11, activating phospholipase C and increasing intracellular calcium, which triggers GH release from somatotroph cells.

Notably, GHSR-1a has high constitutive activity — it signals even without ligand binding, contributing to baseline appetite and GH pulsatility. This constitutive activity can be modulated by inverse agonists, making GHSR a pharmacologically complex target.

Relevance to Peptide Research

GHSR is the primary target for several research peptides including MK-677 (ibutamoren), GHRP-6, GHRP-2, hexarelin, and ipamorelin. These growth hormone secretagogues bind GHSR-1a to stimulate pulsatile GH release, mimicking the action of endogenous ghrelin but with varying selectivity profiles. Understanding GHSR pharmacology is essential for interpreting research on GH-axis peptides.

Related Peptides

Peptide profiles that reference “GHSR” in their research content.