Ghrp- 6

GHRP-6 is a synthetic, 6-amino acid peptide (His-D-Trp-Ala-Trp-D-Phe-Lys-NH2) belonging to the first generation of growth hormone secretagogues (GHS). I

t was the first synthetic peptide discovered with potent, dose-dependent growth hormone (GH)-releasing activity. It functions as a specific and potent agonist for the ghrelin/growth hormone secretagogue receptor (GHSR-1a).

While its primary research application involves stimulating GH release, it possesses a broader spectrum of biological activities than later, more selective analogs.

• Direct Pituitary Action: GHRP-6 binds with high affinity to GHSR-1a on somatotrophs in the anterior pituitary, activating the Gq/11-phospholipase C pathway. This leads to increased inositol trisphosphate (IP3), diacylglycerol (DAG), and intracellular calcium, triggering GH exocytosis.

• Central Hypothalamic Action: It also acts on GHSR-1a in the arcuate nucleus and ventromedial hypothalamus, resulting in:

  Suppression of Somatostatin (GHIH) secretion.

  Stimulation of Growth Hormone-Releasing Hormone (GHRH) release.

• Synergistic GH Release: This combined action—direct pituitary stimulation plus hypothalamic modulation—produces a powerful, synergistic release of GH that exceeds the additive effect of GHRH and GHRP-6 administered separately.

• Corticotropic & Prolactin Effects: At effective GH-releasing doses, GHRP-6 also stimulates a notable release of adrenocorticotropic hormone (ACTH), cortisol/corticosterone, and to a lesser extent, prolactin, via mechanisms likely involving the hypothalamus.