Hyperaldosteronism: Overproduction of the hormone aldosterone from the outer portion (cortex) of the adrenal gland or a tumor containing that type of tissue. Excess aldosterone (pronounced al-do-ster-one) results in low potassium levels (hypokalemia), underacidity of the body (alkalosis), muscle weakness, excess thirst (polydipsia), excess urination (polyuria), and high blood pressure (hypertension). Also called aldosteronism and Conn's syndrome.