Sermorelin (GHRH 1-29 NH₂) is a synthetic 29-amino acid peptide corresponding to the biologically active N-terminal fragment of endogenous growth hormone-releasing hormone (GHRH). Endogenous GHRH is a 44-amino acid hypothalamic peptide — Sermorelin retains the receptor-binding domain responsible for GHRH's physiological effects while being shorter and more stable than the full-length sequence.
It acts as a selective agonist of the GHRH receptor (GHRHR), a Gs-coupled receptor expressed on pituitary somatotroph cells. Receptor activation increases intracellular cAMP, activates protein kinase A, and stimulates the pulsatile secretion of endogenous growth hormone — closely mimicking the natural hypothalamic GHRH pulse.
Sermorelin's mechanism is straightforward: it binds the GHRH receptor on anterior pituitary somatotrophs, activates the Gs → adenylyl cyclase → cAMP → PKA signaling cascade, and triggers GH release in a pulsatile pattern consistent with endogenous GHRH physiology.
Short half-life as a research feature: With a half-life of approximately 10–20 minutes, Sermorelin produces a discrete, time-limited GH pulse that closely mirrors the natural hypothalamic GHRH pulse. This makes it particularly useful in research protocols where investigators want to model native GHRH kinetics — as opposed to CJC-1295 with DAC (~6–8 day half-life), which produces sustained, tonic GHRHR occupancy and a fundamentally different GH secretion pattern.
Complementary to GHRPs: Sermorelin (GHRHR agonist) and GHRPs like Ipamorelin (GHSR-1a agonist) act on different receptors via different second-messenger systems. Sermorelin amplifies pulse amplitude via the GHRH pathway; Ipamorelin triggers GH release via the ghrelin receptor pathway. Researchers studying the convergent activation of both systems use both compounds together. See: Ipamorelin vs CJC-1295 comparison →