Cortisol metabolism and the role of 11β-hydroxysteroid dehydrogenase

Two isoforms of the enzyme 11β-hydroxysteroid dehydrogenase (11β-HSD) interconvert the active glucocorticoid, cortisol, and inactive cortisone. 11β-HSD1 is believed to act in vivo predominantly as an oxo-reductase using NADP(H) as a cofactor to generate cortisol. In contrast, 11β-HSD2 acts exclusively as an NAD-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 11β-HSD2 is implicated in patients with hypertension and intra-uterine growth retardation, while 11β-HSD1 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 11β-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.