Aldosterone belongs to a class of hormones called mineralocorticoids, also produced by the adrenal glands. Aldosterone helps maintain blood pressure and water and salt balance in the body by helping the kidney retain sodium and excrete potassium. When aldosterone production falls too low, the kidneys are not able to regulate salt and water balance, causing blood volume and blood pressure to drop.
Addison's disease occurs due to the destruction of the adrenal cortex. As a result, both cortisol and aldosterone hormones are often lacking. Addison's disease symptoms usually begin when at least 90 percent of the adrenal cortex has been destroyed.
In about 70 percent of Addison's disease cases, the destruction of the adrenal cortex is caused by the body's own immune system (autoimmune disease). Normally the immune system protects the body against infection and disease. In an autoimmune disease, the body's immune system mistakenly attacks some part of the body. In Addison's disease, the immune system attacks the adrenal cortex. Why the immune system attacks the adrenal cortex is unknown.
Other causes of Addison's disease can include:
- Chronic infection (mainly fungal infections)
- Cancer cells spreading from other parts of the body to the adrenal glands (especially breast cancer)
- Surgical removal of the adrenal glands.
(Click Causes of Addison's Disease for more information.)