There are normally two adrenal glands, located above each kidney. However, the absence of the adrenal medulla and epinephrine does not cause disease. In contrast, the outer portion of the adrenal, the cortex, is more critical. The adrenal cortex makes two important steroid hormones, cortisol and aldosterone. Cortisol mobilizes nutrients, modifies the body's response to inflammation, stimulates the liver to raise the blood sugar, and also helps to control the amount of water in the body.
Aldosterone regulates salt and water levels which affects blood volume and blood pressure.
Classical Addison's disease results from a loss of both cortisol and aldosterone secretion due to the near total or total destruction of both adrenal glands. This condition is also called primary adrenal insufficiency. If ACTH is deficient, there will not be enough cortisol produced, although aldosterone may remain adequate. This is secondary adrenal insufficiency, which is distinctly different, but similar to Addison's disease, since both include a loss of cortisol secretion. When Dr. Thomas Addison's' first described this disease in London in 1855, the most common cause was tuberculosis.