Cytosolic aldo-keto reductase that catalyzes the NADH and NADPH-dependent reduction of ketosteroids to hydroxysteroids. Acts as a NAD(P)(H)-dependent 3-, 17- and 20-ketosteroid reductase on the steroid nucleus and side chain and regulates the metabolism of androgens, estrogens and progesterone (PubMed:
10622721, PubMed:
11165022, PubMed:
7650035, PubMed:
9415401, PubMed:
9927279). Displays the ability to catalyze both oxidation and reduction in vitro, but most probably acts as a reductase in vivo since the oxidase activity measured in vitro is inhibited by physiological concentration of NADPH (PubMed:
14672942, PubMed:
11165022). Acts preferentially as a 17- ketosteroid reductase and has the highest catalytic efficiency of the AKR1C enzyme for the reduction of delta4-androstenedione to form testosterone (PubMed:
20036328). Reduces prostaglandin (PG) D2 to 11beta-prostaglandin F2, progesterone to 20alpha-hydroxyprogesterone and estrone to 17beta-estradiol (PubMed:
15047184, PubMed:
20036328, PubMed:
10622721, PubMed:
11165022, PubMed:
10998348, PubMed:
19010934). Catalyzes the transformation of the potent androgen dihydrotestosterone (DHT) into the less active form, 5-alpha-androstan-3-alpha,17-beta-diol (3-alpha-diol) (PubMed:
10998348, PubMed:
14672942, PubMed:
11165022, PubMed:
7650035, PubMed:
9415401, PubMed:
10557352). Displays also retinaldehyde reductase activity toward 9-cis-retinal (PubMed:
21851338).
