Catalyzes the conversion of 17-oxosteroids to 17beta-hydroxysteroids (PubMed:32557858). Favors the reduction of androstenedione to testosterone (PubMed:32557858). Testosterone is the key androgen driving male development and function (PubMed:32190925, PubMed:32557858). Uses NADPH while the two other EDH17B enzymes use NADH (By similarity). 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 (PubMed:32190925, PubMed:32557858). 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. Expressed in the testes. Expression is restricted to Sertoli cells in fetal life, peaks in neonatal mice, declines thereafter until the age of 21 days, and appears in Leydig cells in adulthood. Null males have increased circulating luteinizing hormone (LH) levels (PubMed:32557858). Null males present mild hypogonadism at adulthood represented by lowered weight of testes and several other androgen-sensitive tissues, a shortened anogenital distance, delayed puberty, and subfertility (fewer litters) (PubMed:32190925). No phenotypic alterations in the null female (PubMed:32190925, PubMed:32557858). Belongs to the short-chain dehydrogenases/reductases (SDR) family. 17-beta-HSD 3 subfamily.