Addison's disease is a disorder that gradually destroys the adrenal glands, causing them to produce insufficient amounts of certain hormones. The body has two adrenal glands, one located on top of each kidney. The most common cause of Addison's disease is an autoimmune disorder in which the body's immune system attacks and destroys the adrenal glands. Other causes of Addison's disease include cancer, infectious diseases such as tuberculosis, and such fungal diseases as histoplasmosis. Addison's disease is named after the British doctor Thomas Addison, who first described the disorder in 1855.