Hexarelin and CJC-1295 without DAC (Mod GRF 1-29) are synthetic research peptides that are used together in experimental models to study the regulation of the growth hormone axis and somatotropic signaling pathways. Hexarelin is a potent hexapeptide growth hormone secretagogue that binds to the growth hormone secretagogue receptor (GHS-R1a) and activates a Gq/PLC-dependent calcium signaling involved in GH release and hypothalamic-pituitary feedback mechanisms. CJC-1295 without DAC is a stabilized analogue of growth hormone-releasing hormone (GHRH 1-29), which selectively activates the GHRH receptor and stimulates adenylate cyclase as well as cAMP-mediated signals in pituitary somatotrophs. Preclinical research utilizes the combined activation of GHS-R1a and GHRH receptors to study synergistic GH secretion, receptor pharmacology and endocrine signaling dynamics in controlled laboratory environments.