The eutopic endometrium in endometriosis: are the changes of clinical significance?

The eutopic endometrium in women suffering from endometriosis is different in many ways from that of healthy controls. Both proliferative and secretory eutopic endometria exhibit changes in endometriosis with heterogeneous responses. In addition, nerve fibres appear in the endometrium and myometrium of these women. The endometrium is a rich source of pro-angiogenic factors and vascular events are often disrupted in endometriosis with an overall increase in angiogenesis. A number of investigations have shown that endometriosis is likely the most common cause of endometrial receptivity defects. Endometriosis is also associated with relative 17β-hydroxysteroid dehydrogenase type II deficiency and these molecular aberrations indicate that local oestrogen production sustains ectopic implants. Recently it has been shown that endometriosis, as a chronic inflammatory disorder, disrupts co-ordinated progesterone response throughout the reproductive tract, including the endometrium, leading to a condition of ‘progesterone resistance’. Investigators have searched for biomarkers of endometriosis, but these investigations are fraught with methodological difficulties. In conclusion, molecular phenotyping of the endometrium is changing the disease paradigm, from being foremost an oestrogen-dependent disease to a disorder characterized primarily by progesterone resistance.In recent years, research on the pathogenesis of endometriosis has been focused on alterations in the uterus and particularly the eutopic endometrium. The eutopic endometrium in women suffering from endometriosis is different in many ways from that of healthy controls. Both proliferative and secretory eutopic endometria exhibit changes in endometriosis with heterogeneous responses. The endometrium is a rich source of pro-angiogenic factors and vascular events are often disrupted in endometriosis with an overall increase in angiogenesis. A number of investigations have shown that endometriosis is likely the most common cause of endometrial receptivity defects. Recently, it has been shown that endometriosis, as a chronic inflammatory disorder, disrupts co-ordinated progesterone response throughout the reproductive tract, including the endometrium, leading to a condition of ‘progesterone resistance’. Investigators have searched for biomarkers of endometriosis, but these investigations are fraught with methodological difficulties. In conclusion, molecular phenotyping of the endometrium is changing the disease paradigm; from being foremost an oestrogen-dependent disease to a disorder characterized primarily by progesterone resistance.