Cortisol is the adrenal-cortex hormone that helps the human body respond to long-term stress.
It is a steroid hormone produced in the zona fasciculata, one of the layers of the adrenal cortex. Cortisol helps regulate metabolism, making energy available during demanding situations, and influences immune activity, blood pressure, and the body's response to inflammation.
Its production is controlled by the hypothalamic-pituitary-adrenal axis. The hypothalamus releases CRH, which prompts the pituitary gland to release ACTH; ACTH then stimulates the adrenal cortex to produce cortisol. Rising cortisol levels normally provide negative feedback that reduces further CRH and ACTH release.
Cortisol follows a daily rhythm, usually reaching its highest level around waking and declining later in the day. It is often confused with adrenaline, which is produced mainly by the adrenal medulla and acts more rapidly during acute emergencies. Persistently excessive or insufficient cortisol can cause serious medical disorders.