Increased Production of 17β-Estradiol in Endometriosis Lesions is The Result of Impaired Metabolism

Context: substantial evidence suggests that the expression of steroid metabolizing enzymes in endometriosis is altered, turning the ectopic endometrium into a source of 17β-estradiol. However, whether these differences result in a net increase in local 17β-estradiol production/activity has not been shown. Subjects and Methods: The activities of the most important steroidogenic enzymes synthesizing and inactivating 17β-estradiol were determined by HPLC in matched eutopic and ectopic tissue from patients with endometriosis (n = 14) and in endometrium from controls (n = 20). Results: Aromatase activity is negligible in the ectopic endometrium, whereas the activity of estrogen sulfatase is high though not different between ectopic, eutopic and control endometrium. The activity of 17β-hydroxysteroid dehydrogenases (17β-HSDs) converting estrone into 17β-estradiol is higher in the ectopic compared to the eutopic endometrium in patients. The activity of 17β-HSDs converting 17β-estradiol back to estrone is signifi...