17ò-Hydroxysteroid dehydrogenase 2 (17ò-HSD2) is an enzyme of the 17ò-hydroxysteroid dehydrogenase (17ò-HSD) family that in humans is encoded by the HSD17B2 gene.
17ò-HSD2 is involved in inactivation of androgens and estrogens, being accurately describable as "antiandrogenic" and "antiestrogenic", and is the key 17ò-HSD isozyme in androgen and estrogen inactivation. Specific reactions catalyzed by 17ò-HSD2 include estradiol to estrone, testosterone to androstenedione, and androstenediol to . In addition to 17ò-HSD activity, this enzyme also shows high 20ñ-hydroxysteroid dehydrogenase activity and can activate the weak progestogen 20ñ-hydroxyprogesterone into the potent progestogen progesterone.
17ò-HSD2 is widely expressed throughout the body including in the placenta, liver, intestines, endometrium, kidney, pancreas, breast, prostate, bone, and many other tissues.
Polymorphisms in HSD17B2 have been associated with breast cancer and prostate cancer. 17ò-HSD2 activity has also been associated with endometriosis and osteoporosis, and inhibitors of the enzyme are of potential interest in the treatment of the latter condition. Inactivating mutations resulting in a syndrome of congenital deficiency of 17ò-HSD2 have not been reported to date.