The syndrome of apparent mineralocorticoid excess (AME) is a rare disorder identified in approximately 50 individuals characterized by low-aldosterone hypertension, associated with low renin and hypokalemia These subjects avidly retain salt and water, have suppression of both plasma renin and aldosterone levels, but clinically appear as though they have a state of mineralocorticoid excess. A detailed series of investigations has elucidated the cause of this syndrome: severe attenuation of the enzyme 11 beta-hydroxysteroid dehydrogenase (11-beta-HSD). 11-beta-HSD converts cortisol, able to activate mineralocorticoid receptors to cortisone, which cannot. This abnormality can be identified by measuring an abnormal ratio of urinary breakdown products of cortisol and cortisone. Subjects with AME have a high ratio indicative of elevated cortisol concentrations.