Addison's disease [for Thomas Addison], progressive disease brought about by atrophy of the outer layer, or cortex, of the adrenal gland; it is also called chronic adrenocortical insufficiency. The deterioration of this tissue causes a decrease in the secretion of steroid hormones, many of which are necessary for the maintenance of life. In many cases the cause of the wasting process is not known; in others the predominant cause is the formation and infiltration of tumors, inflammatory disease, or surgery. Symptoms are increasing weakness, abnormal pigmentation of the skin and mucous membranes, weight loss, low blood pressure, dehydration, and gastrointestinal upsets. Secondary Addison's disease is most commonly caused by acute withdrawal of steroids. Once considered inevitably fatal, Addison's disease can now be treated with injections of adrenocortical hormones.