There are at least 2 isoforms of 11-beta-HSD. The first discovered, HSD11B1, was purified (Lakshmi and Monder, 1988) and cloned (Agarwal et al., 1989) from rat liver. This glycoprotein enzyme (also called type I) catalyzes both 11-beta-dehydrogenation and the reverse 11-oxoreduction reaction. The enzyme and corresponding mRNA have been detected in a wide range of rat and human tissues, including liver, lung, and testis. The other isoform, type II, is expressed predominantly in the kidney and placenta and catalyzes only the 11-beta-dehydrogenation reaction; see HSD11B2 (614232).