Catalyzes the NAD-dependent oxidation of highly active 17beta-hydroxysteroids, such as estradiol (E2), testosterone (T), and dihydrotestosterone (DHT), to their less active forms and thus regulates the biological potency of these steroids. Oxidizes estradiol to estrone, testosterone to androstenedione, and dihydrotestosterone to 5alpha-androstan-3,17-dione. Also has 20-alpha-HSD activity. 17beta-estradiol + NAD(+) = estrone + H(+) + NADH NAD(+) + testosterone = androst-4-ene-3,17-dione + H(+) + NADH 17beta-hydroxy-5alpha-androstan-3-one + NAD(+) = 5alpha-androstan-3,17-dione + H(+) + NADH (20S)-hydroxypregn-4-en-3-one + NAD(+) = H(+) + NADH + progesterone Homodimer. Belongs to the short-chain dehydrogenases/reductases (SDR) family.