3-alpha-hydroxysteroid dehydrogenase that converts 3-alpha-tetrahydroprogesterone (allopregnanolone) to dihydroxyprogesterone and 3-alpha-androstanediol to dihydroxyprogesterone. Also plays a role in the biosynthesis of retinoic acid from retinaldehyde. Can utilize both NADH and NADPH. 3beta-hydroxy-5alpha-pregnane-20-one + NAD(+) = 5alpha-pregnane-3,20-dione + H(+) + NADH 17beta-hydroxy-5alpha-androstan-3-one + NAD(+) = 5alpha-androstan-3,17-dione + H(+) + NADH 3alpha-hydroxy-5alpha-androstan-17-one + NAD(+) = 5alpha-androstan-3,17-dione + H(+) + NADH 5alpha-androstane-3alpha,17beta-diol + NAD(+) = 17beta-hydroxy-5alpha-androstan-3-one + H(+) + NADH all-trans-retinol + NAD(+) = all-trans-retinal + H(+) + NADH 3alpha-hydroxy-5alpha-pregnan-20-one + NAD(+) = 5alpha-pregnane-3,20-dione + H(+) + NADH Homotetramer. Belongs to the short-chain dehydrogenases/reductases (SDR) family.