HPA Axis (Stress Response)
Hypothalamic-pituitary-adrenal axis regulating cortisol and stress response.
Overview
The HPA axis is the central stress response system. Stress stimulates hypothalamic CRH release, which triggers ACTH secretion from the anterior pituitary. ACTH stimulates the adrenal cortex to produce cortisol (corticosterone in rodents). Cortisol has widespread metabolic, immune, and CNS effects. Negative feedback at the hypothalamus and pituitary normally limits cortisol production. The axis follows circadian rhythmicity with peak cortisol in the morning.
Cellular Location
Hypothalamus → Pituitary → Adrenal cortex
Clinical Significance
Chronic stress/HPA dysregulation linked to depression, PTSD, metabolic syndrome; Cushing syndrome = cortisol excess; Addison disease = cortisol deficiency; glucocorticoids widely used as anti-inflammatory drugs.