Expression of 11 beta-hydroxysteroid dehydrogenase in early pregnancy: Implications in human trophoblast-endometrial interactions

Glucocorticoid hormone action in target tissues is modulated by 11 beta-hyd roxysteroid dehydrogenase (11 beta-HSD), which interconverts active cortiso l and corticosterone and their inert 11-keto metabolites, cortisone and 11- dehydrocovticosterone. Two different 11 beta-HSD isoforms exist: a low-affi nity NADP-dependent dehydrogenase/oxoreductase (11 beta-HSD1) and a high-af finity NAD-dependent dehydrogenase (11 beta-HSD2). This brief review descri bes the expression and distribution of 11 beta-HSD isoforms in human placen ta. In particular, it discusses the results of studies dealing with the exp ression of 11 beta-HSD activity in experimental models representative of th e fetomaternal interface in the early gestation. The findings have implicat ions in terms of protection of the fetus against corticosteroid toxicity an d modulation of active glucocorticoid levels and their biological effects i n early pregnancy.