Cortisol is a corticosteroid hormone produced by the Zona fasciculata of the adrenal cortex (in the adrenal gland). It is a vital hormone that is often referred to as the "stress hormone" as it is involved in the response to stress. It increases blood pressure, blood sugar levels and has an immunosuppressive action. In pharmacology, the synthetic form of cortisol is referred to as hydrocortisone, and is used as an antagonist in the treatment of allergies and inflammation as well as substitute supplementation in cortisol production deficiencies. When first introduced as a treatment for rheumatoid arthritis, it was referred to as Compound E.