Aldosterone is closely involved in certain hypertensive disorders. Increased, nonsuppressible levels of aldosterone and reduced plasma renin activity are diagnostic of primary hyperaldosteronism. Sodium loading is an effective screening process for detection of the hypokalemia characteristic of this disorder. Secondary hyperaldosteronism is most frequently associated with increases in activity of the renin-angiotensin system, usually resulting from renovascular disorders; hypertension and complications are usually more severe. High levels of plasma renin activity and elevated, suppressible aldosterone levels are characteristic.