The brain’s signal to the pituitary to release growth hormone — the endogenous molecule that sermorelin and CJC-1295 mimic.Produced in the hypothalamus; acts on GHRH receptors (GHRHRs) on pituitary somatotrophs to stimulate GH synthesis and secretion. Sermorelin (29-amino acid synthetic GHRH fragment) and Modified GRF(1-29)/CJC-1295 are synthetic GHRH analogs acting via the same receptor. Distinct from ghrelin and the GHS-R1a pathway — a second independent GH secretagogue mechanism. The two-pathway system explains the pharmacological rationale for GHRH analog + GHRP combination protocols.