Can convert prostaglandin E2 to prostaglandin F2-alpha. NADP(+) + prostaglandin F2alpha = H(+) + NADPH + prostaglandin E2 (17R,20S)-17,20-dihydroxypregn-4-en-3-one + NADP(+) = 17alpha-hydroxyprogesterone + H(+) + NADPH (17R,20S)-17,20-dihydroxypregn-4-en-3-one + NAD(+) = 17alpha-hydroxyprogesterone + H(+) + NADH Belongs to the aldo/keto reductase family.