Sermorelin is the structurally truncated analog of Growth Hormone Releasing Hormone (GHRH). It consists of the first 29 amino acids of the naturally occurring neurohormone that is produced in the hypothalamus. Sermorelin is the most widely used member of the GHRH analogue drug class. It can significantly promote the synthesis and release of growth hormone (GH) from cells in the pituitary gland, improving the serum concentrations of GH and subsequently insulin-like growth factor 1 (IGF-1) in animals and humans. It is able to influence the concert of hormonal signals that affect GH secretion from the anterior pituitary including GHRH, somatostatin, and insulin like growth factor (IGF) and others. The positive and negative opposing regulation of growth hormone by GHRH and somatostatin, respectively, creates a rhythmic-circadian pattern of GH secretion. Thus, modification of both pulse amplitude and frequency of GH secretion results from Sermorelin administration. After sermorelin stimulates the release of GH from the pituitary gland, it increases synthesis of IGF-1 in the liver and peripheral tissues.
Sermorelin acts on the growth hormone releasing hormone receptor (GHRHr) in the pituitary to regulate cellular activities. GHRHr is the natural receptor for the endogenous hormone, GHRH, and for sermorelin. This receptor regulates growth hormone release directly by stimulation and indirectly by a feedback relationships with somatostatin.
Sermorelin is readily degraded after reaching the bloodstream, having a biological half-life of approximately 10-20 min. Due to the biological half-life and bioavailability of Sermorelin, administration for growth in childhood GHD must occur periodically several times a day as subcutaneous-injections. However, single daily dosing is sufficient to treat most cases of adult-onset GH insufficiency. Three (3) mcg/kg subcutaneous-injections of Sermorelin have been reported to simulate a naturally occurring GHRH mediated GH release responses.
In addition to increasing production and secretion GHRH also affects sleep patterns by increasing the amount of slow wave sleep (SWS) while augmenting sleep-related GH secretion and reducing cortisol secretion.
To exert all its beneficial effects, Sermorelin requires a functioning pituitary and a host of peripheral tissues. This is due to the reliance on endogenous receptors controlling hormone secreting glands and tissues. More precisely, functioning growth hormone releasing hormone receptors (GHRHr) are required on somatotrophs in a functioning anterior pituitary.