Secretagogue
A substance that stimulates secretion of a hormone or other molecule from a cell. In peptide therapeutics, the term most commonly refers to growth hormone secretagogues (tesamorelin, GHRP compounds) and insulin secretagogues (GLP-1 receptor agonists stimulate glucose-dependent insulin release).
Technical Context
Secretagogues stimulate hormone release through receptor activation on the secreting cell. Growth hormone secretagogues: GHRH receptor agonists (tesamorelin, Mod GRF 1-29) stimulate GH via cAMP/PKA pathway on somatotrophs; GHS-R1a agonists (GHRPs, ipamorelin) stimulate GH via IP3/DAG/calcium pathway. The two pathways are synergistic — combined GHRH + GHRP produces greater GH release than either alone (this synergy is exploited in some research peptide protocols). Insulin secretagogues: GLP-1 RAs stimulate insulin release by potentiating glucose-stimulated insulin secretion via cAMP/Epac2 on beta cells — crucially, this is glucose-dependent (no insulin release at low glucose), reducing hypoglycaemia risk vs sulfonylureas (which stimulate insulin release regardless of glucose level). Calcitonin secretagogues: GLP-1R activation on rodent C-cells stimulates calcitonin release — this is the mechanism behind the C-cell tumour signal in rodent studies.