20-Alpha-Hydroxysteroid Dehydrogenase (HSD20a)

20aHSD belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. On a functional level, ovarian 20alpha-HSD is actively involved in the control of progesterone homeostasis in pregnancy of rats and mice. While 20alpha-HSD expression and activity is downregulated in the corpus luteum of pregnancy, 24 hrs prior to parturition ovarian 20alpha-HSD activity is acutely stimulated. Accordingly, in mice with targeted deletion of the 20alpha-HSD gene, progesterone blood concentration remain high throughout pregnancy which results in a delay of 2-4 days in parturition. Indicating that expression of 20alpha-HSD activity is mandatory for the induction of parturition through reduction of progesterone blood concentration.In mice, 20alpha-HSD is also expressed in the adrenals, kidneys, brain, thymus, T cells and bone marrow.