Favors the reduction of estrogens and androgens. Converts estrone (E1) to a more potent estrogen, 17beta-estradiol (E2) (PubMed:8994190). Also has 20-alpha-HSD activity. Uses preferentially NADH. . This is the function of Ensembl gene identifier ENSG00000108786 (HSD17B1, hydroxysteroid 17-beta dehydrogenase 1).