Growth Hormone-Releasing Hormone (GHRH)
A 44 amino acid peptide hormone produced by the hypothalamus that stimulates growth hormone release from the anterior pituitary gland. GHRH is the primary physiological stimulator of growth hormone secretion and has a very short half-life of approximately 7 minutes. Tesamorelin is a synthetic GHRH analogue.
Technical Context
GHRH is a 44 amino acid peptide (GHRH(1-44)-NH2) released from arcuate and ventromedial nuclei of the hypothalamus in a pulsatile pattern. It travels via the hypothalamic-hypophyseal portal system to the anterior pituitary, binding GHRH receptors (a GPCR) on somatotroph cells. Receptor activation increases intracellular cAMP, stimulating both GH gene transcription and GH vesicle secretion. Natural GHRH has a half-life of approximately 7 minutes due to rapid cleavage by DPP-4 (at position 2) and other plasma proteases. The biologically active fragment is GHRH(1-29), and Modified GRF(1-29) is a research analogue with amino acid substitutions at positions 2, 8, 15, and 27 to resist DPP-4 and improve stability.