Addison's disease, which is also known as Addison disease or primary adrenal insufficiency, is an illness in which the adrenal glands stop producing hormones that are important for certain bodily functions. The most common cause of Addison's disease is an autoimmune disease; other causes of this disease include tuberculosis and chronic infection. Common symptoms of Addison's disease include chronic fatigue, muscle weakness, and loss of appetite. Addison's disease, though incurable, is a condition that can be treated and controlled with medication.