Addison disease is an uncommon, but potentially catastrophic endocrine disorder affecting the adrenal glands. In Addison disease, the adrenal glands, which sit above the kidneys, do not produce enough of the hormones cortisol and aldosterone. The disease causes muscle weakness, fatigue, weight loss, abnormal balance of salt and potassium, low blood pressure and skin changes.
Most cases of Addison disease not due to chronic steroid use are caused by the gradual destruction of the adrenal cortex by the body's own immune system. About 70% of reported cases of Addison disease are caused by autoimmune disorders, in which the immune system makes antibodies that attack the body's own tissues or organs, slowly destroying them. Adrenal insufficiency occurs when at least 90% of the adrenal cortex has been destroyed. As a result, often both glucocorticoid (cortisol) and mineralocorticoid (aldosterone) hormones are lacking. Sometimes only the adrenal gland is affected, as in idiopathic adrenal insufficiency. Sometimes other glands also are affected, as in the polyendocrine deficiency syndrome.
Tuberculosis (TB) is caused by the bacterium Mycobacterium tuberculosis, which is the most common infectious cause of Addison disease. It accounts for about 20 percent of cases of primary adrenal insufficiency in developed countries. When adrenal insufficiency was first identified in the mid-19th century, TB was found at autopsy in 70%–90% of cases. As the treatment for TB improved, however, the incidence of adrenal insufficiency due to TB of the adrenal glands has greatly decreased. TB is making a comeback, however, so Addison disease due to TB may become more common in future years.