Sermorelin

Sermorelin is a synthetic 29-amino acid peptide corresponding to the first 29 amino acids of native human growth hormone-releasing hormone (GHRH 1-44). It was the first GHRH analog to be FDA-approved (1997) for the diagnostic evaluation of pituitary GH secretory capacity and for the treatment of growth hormone deficiency in children (marketed as Geref). The first 29 amino acids of GHRH contain the full biological activity of the 44-amino acid native hormone, as established by structure-activity studies. Sermorelin represents the unmodified (native sequence) truncated GHRH, in contrast to modified analogs like CJC-1295 which contain amino acid substitutions for enhanced stability. Sermorelin has a relatively short half-life (~10-20 minutes) and is susceptible to DPP-IV cleavage, which led to the development of stabilized analogs. Despite this, sermorelin remains an important reference compound in GHRH receptor pharmacology.

Sermorelin has been investigated for its agonist activity at the GHRH receptor on anterior pituitary somatotroph cells. The GHRH receptor is a Gs-coupled GPCR that, upon activation by sermorelin, stimulates adenylyl cyclase and increases intracellular cAMP. This PKA-dependent signaling promotes GH gene transcription, GH synthesis, and exocytosis of GH-containing secretory granules. Researchers observed that sermorelin produces physiological pulsatile GH release patterns, preserving the normal feedback regulation of the GH axis. The peptide’s short half-life (~10-20 minutes due to DPP-IV cleavage at the Ala2-Asp3 bond) results in transient GHRH receptor activation, which actually mimics the natural episodic pattern of hypothalamic GHRH release. Studies suggest that pulsatile GHRH receptor stimulation maintains somatotroph responsiveness better than continuous stimulation, which can lead to receptor desensitization. Sermorelin also acts synergistically with GHSR agonists at the pituitary level.

Clinical Use

Prakash and Goa (1999) reviewed sermorelin’s clinical pharmacology, including its FDA-approved indications for GH deficiency diagnosis and treatment, and characterized its GH-releasing activity and safety profile [1].

GHRH Structure-Activity

Ling et al. (1984) established that the first 29 amino acids of GHRH contain full biological activity, providing the rationale for sermorelin as a truncated GHRH analog [2].

Pulsatile GH Release

Jaffe et al. (1993) investigated sermorelin’s effects on GH pulse dynamics and demonstrated that intermittent administration maintains physiological GH pulsatility, supporting its use as a more physiological approach to GH stimulation [3].