Corticotropin-Releasing Hormone (CRH)
A 41 amino acid peptide produced by the hypothalamus that stimulates ACTH release from the anterior pituitary, initiating the HPA axis stress response cascade. CRH is the upstream signal that drives cortisol production. Dysregulation of CRH signalling is implicated in mood disorders and stress-related conditions.
Technical Context
CRH (41 aa) is the primary activator of the HPA stress axis. It is produced in the paraventricular nucleus of the hypothalamus and released into the portal blood system. CRH binds CRH-R1 (Gαs-coupled) on pituitary corticotrophs, stimulating POMC transcription and ACTH secretion. CRH also binds CRH-R2 in the brain and periphery, involved in appetite suppression, anxiety, and immune modulation. CRH secretion follows a circadian rhythm (peaking in early morning) and is stimulated by physical and psychological stress. Cortisol provides negative feedback inhibition of CRH release. Ovine CRH is used diagnostically (CRH stimulation test) to differentiate pituitary from ectopic ACTH sources in Cushing's syndrome evaluation.