A 17alpha-hydroxy-C21-steroid that is pregn-4-ene substituted by oxo groups at positions 3 and 20 and hydroxy groups at positions 11, 17 and 21. Cortisol is a corticosteroid hormone or glucocorticoid produced by zona fasciculata of the adrenal cortex, which is a part of the adrenal gland. It is usually referred to as the "stress hormone" as it is involved in response to stress and anxiety, controlled by corticotropin-releasing hormone (CRH). It increases blood pressure and blood sugar, and reduces immune responses