11 beta-Hydroxysteroid-dehydrogenase isoforms: tissue distribution and implications for clinical medicine

11 beta -hydroxylation is essential for glucocorticoid and mineralocorticoi d activity of a steroid. The enzyme catalyzing this reaction is termed 11 b eta -hydroxysteroid-dehydrogenase (11 beta -HSD). Two isoenzymes of 11 beta -HSD have been characterized in human tissues. Whereas 11 beta -HSD-I work s mainly as a reductase, 11 beta -HSD-II only functions as an oxidizing (in activating) enzyme for physiological glucocorticoids. Thus, the tissue dist ribution of both enzymes plays a crucial role for the specific glucocortico id status of an organ. This review summarizes our knowledge of tissue distr ibution of both 11 beta -HSD isoenzymes, their physiological function and p athophysiological role in certain clinical abnormalities, and their relevan ce to the metabolism of synthetic glucocorticoid and mineralocorticoid comp ounds.