Expression of the 17β-hydroxysteroid dehydrogenase type 5 mRNA in the human brain

Abstract An enzyme-mediated metabolism of androgens and estrogens including 17β-HSD activity in the brain of vertebrates was discovered ∼30 years ago. Mainly 5α-reductase and aromatase have been studied in detail. Recently we could demonstrate reductive and oxidative 17β-HSD activity as well as considerable mRNA expression of the 17β-HSD types 3 and 4 in the human brain. In the present study, we report on 17β-HSD type 5 mRNA expression in brain tissue of women and men. Data analysis did not reveal sex specific differences, but we determined a significantly higher mRNA concentration in the subcortical white matter (SC) than in the cerebral cortex (CX). Investigation of reductive 17β-HSD in vitro activity with 2 μM androstenedione as the substrate revealed no sex specific differences. Testosterone formation was significantly higher in SC than in CX. Moreover, enzyme activity was significantly higher in brain tissue of adults compared to that of children.