Growth hormone-releasing factor receptor (GHRHR)

The growth hormone-releasing factor receptor (GHRHR) is a G-protein-coupled receptor primarily expressed in the anterior pituitary gland. It binds growth hormone-releasing hormone (GHRH) to stimulate the synthesis and release of growth hormone (GH). This process regulates body size, metabolism, and proliferation/differentiation of somatotroph cells. Mutations are associated with isolated growth-hormone deficiency. It signals through cAMP-dependent and Phospholipase C pathways.

Binding of GHRH activates Gs protein, leading to increased cAMP and PKA activation, ultimately increasing GH gene transcription and release. Activation via βγ-complex leads to PLC activation, DAG & IP3 production, IP3 increases intracellular Ca²⁺ causing vesicle fusion & GH secretion. Opens Na⁺ channels via phosphatidylinositol 4,5-bisphosphate; depolarization opens voltage-dependent Ca²⁺ channels for further GH release.