Catalyzes the conversion of 17-oxosteroids to 17beta-hydroxysteroids. Favors the reduction of androstenedione to testosterone. Testosterone is the key androgen driving male development and function (By similarity). Uses NADPH while the two other EDH17B enzymes use NADH. Androgens such as epiandrosterone, dehydroepiandrosterone, androsterone and androstanedione are accepted as substrates and reduced at C-17. Can reduce 11-ketoandrostenedione as well as 11beta-hydroxyandrostenedione at C-17 to the respective testosterone forms (By similarity). Plays a role in the rate-limiting-step for the maximum level of testosterone production by the testis but does not affect basal testosterone production (By similarity). a 17beta-hydroxy steroid + NADP(+) = a 17-oxo steroid + H(+) + NADPH NADP(+) + testosterone = androst-4-ene-3,17-dione + H(+) + NADPH 17beta-estradiol + NADP(+) = estrone + H(+) + NADPH 3beta-hydroxyandrost-5-en-17-one + H(+) + NADPH = androst-5-en-3beta,17beta-diol + NADP(+) 17beta-hydroxy-5alpha-androstan-3-one + NADP(+) = 5alpha-androstan-3,17-dione + H(+) + NADPH 3alpha-hydroxy-5alpha-androstan-17-one + H(+) + NADPH = 5alpha-androstane-3alpha,17beta-diol + NADP(+) 3beta-hydroxy-5alpha-androstan-17-one + H(+) + NADPH = 5alpha-androstane-3beta,17beta-diol + NADP(+) androst-4-ene-3,11,17-trione + H(+) + NADPH = 17beta-hydroxyandrost-4-ene-3,11-dione + NADP(+) 11beta-hydroxyandrost-4-ene-3,17-dione + H(+) + NADPH = 11beta,17beta-dihydroxyandrost-4-ene-3-one + NADP(+) Hormone biosynthesis; testosterone biosynthesis. Steroid metabolism. Belongs to the short-chain dehydrogenases/reductases (SDR) family. 17-beta-HSD 3 subfamily.