17b-hydroxysteroid dehydrogenase type 1 (17b-HSD) catalyzes the final step in the formation of estradiol and testosterone from estrone and androstenedione, respectively. Ovarian granulosa cells and breast tissue both express 17b-HSD. Other tissues that express 17b-HSD include testis, placenta, uterus, prostate and adipose tissue. 17b-HSD functions as a homodimer and prefers NADP(H) over NAD(H) for oxidation and reduction. The gene encoding human 17b-HSD maps to chromosome 17q12-q21. The importance of 17b-HSD to estradiol production suggests the specific inhibition of 17b-HSD may aid in breast cancer therapy. Breast cancer patients with an amplification of 17b-HSD expression statistically have a worse outcome than those without. 17b-HSD amplification in tamoxifen-treated patients correlates to decreased breast cancer survival.
