HSD17B2(17-BETA-HYDROXYSTEROID DEHYDROGENASE II), also called 17-BETA-HSD II, is an anzyme which have 387 amino acids with a predicted molecular weight of 42,782 and associate with the membranes of the endoplasmic reticulum. Its Cytogenetic location is 16q23.3. The type 2 enzyme was capable of catalyzing the interconversion of testosterone and androstenedione, as well as estradiol and estrone. HSD17B2 mRNA was detected in 18 of 42 (43%) adenomas but not in prolactinomas. In the human endometrium, inactivation of 17-beta-estradiol to estrone is catalyzed by HSD17B2.And HSD17B2 activity distinguishing between disease-free and diseased endometria. HSD17B2 efficiently catalyzes the oxidative metabolism of androgens and estrogens, and it is expressed in a large series of human peripheral tissues. The previous paradigm that HSD17B2 activity in the endometrium is elevated during the secretory phase is confined to diseased endometrium but not to disease-free endometrium.