Cortisol is a corticosteroid hormone synthesized by the zona fasciculata of the adrenal cortex, which is a part of the adrenal gland. Cortisol is called the "stress hormone" since it is involved in response to stress and anxiety, controlled by corticotropin-releasing hormone (CRH). Its primary function is to increase blood sugar and stores of sugar in the liver as glycogen, and also suppresses the immune system. Various synthetic forms of cortisol are used to treat a variety of different illnesses. The most well-known of these is a natural metabolic intermediary of cortisol called hydrocortisone. When first introduced as a treatment for rheumatoid arthritis, hydrocortisone was referred to as Compound E.
Cortisol takes part in the following functions: proper glucose metabolism; regulation of blood pressure; insulin release for blood sugar maintanence; immune function; inflammatory response.
The cortisol awakening response (CAR) is an increase of about 50% in cortisol levels occurring 20 to 30 minutes after awakening in the morning in some people. This rise is superimposed upon the late-night rise in cortisol which occurs before awakening. It is thought to be linked to the hippocampus' preparation of the hypothalamic-pituitary-adrenal axis (HPA) to face anticipated stress.