Cortisol metabolsim and the role of 11beta-hydroxysteroid dehydrogenase

Two isoforms of the enzyme 11 beta -hydroxysteroid dehydrogenase (11 beta -HSD) interconvert the active glucocorticoid, cortisol, and inactive cortisone. 11 beta -HSDI is believed to act in vivo predominantly as an oxo-reductase using NADP(H) as a cofactor to generate cortisol. In contrast, 11 beta -HSD2 acts exclusively as an MAD-dependent dehydrogenase inactivating cortisol to cortisone, thereby protecting the mineralocorticoid receptor from occupation by cortisol. In peripheral tissues, both enzymes serve to control the availability of cortisol to bind to the corticosteroid receptors. Defective expression of 11 beta -HSD2 is implicated in patients with hypertension and intra-uterine growth retardation, while 11 beta -HSDI appears to be intricately involved in the conditions of apparent cortisone reductase deficiency, insulin resistance and visceral obesity. The ability of peripheral tissues to regulate corticosteroid concentrations through 11 beta -HSD isozymes is established as an important mechanism in the pathogenesis of diverse human diseases. Modulation of enzyme activity may offer a novel therapeutic approach to treating human disease while circumventing the consequences of systemic glucocorticoid excess or deficiency.