Cortisol and NADP+ react to form cortisone, NADPH, and H+. This reaction is catalyzed by 11beta-hydroxysteroid dehydrogenases 11B1 and B2 (HSD11B1, B2), associated with the endoplasmic reticulum membrane. The conversion of cortisol (CORT), an active hormone, into inactive cortisone (COR) occurs in many tissues in the body, notably in the liver, and appears to play a role in regulating cortisol activity (Tannin et al. 1991, Stewart et al. 1987).