A disease caused by an excess production of the normal adrenal hormone, aldosterone. This hormone is responsible for sodium and potassium balance, which then directly controls water balance to maintain appropriate blood pressure and blood volume. Individuals with a deficiency of aldosterone, especially found in association with a lack of cortisol in Addison's disease, have low blood volume and therefore low blood pressure, low sodium and high potassium. Just the opposite is seen in hyperaldosteronism which causes high blood pressure and low serum potassium. The serum sodium is usually in the normal range. This is a rare disease and is an unusual cause of hypertension. It is usually considered by physicians if they find unexpectedly low potassium in an individual being treated for hypertension. It generally causes no other specific symptoms or signs. The physical examination in people with hyperaldosteronism is totally normal. There are two types of hyperaldosteronism: it can occur from hyperplasia in both adrenal glands or from a benign (rarely malignant) tumor of one of the adrenal glands. When the cause is a single adrenal tumor, it is labeled Conn's Syndrome.