Altered biological characteristics of eutopic and ectopic endometrium

As it has been presented thus far, the pathogenesis of endometriosis is complex and multifactorial. The intrinsic endometrial abnormalities thought to be associated with endometriosis include abnormal gene expression, altered endometrial responses to hormones such as progesterone, impaired immunological response, increased nerve density, and oxidative stress. Also interesting is the fact that such biological alterations have also been observed in the eutopic endometrium of patients with endometriosis, which strongly indicates their critical role in the pathophysiology of the disease. Indeed, it has been suggested that the evaluation of eutopic endometrium is an important line of investigation which may help to achieve a fuller understanding of endometriosis pathogenesis. Hence, we present herein a literature review and a comprehensive evaluation of the involvement of the eutopic endometrium in endometriosis. The biological characteristics of both eutopic and ectopic endometrial tissues as well as their clinical correlations with the disease are highlighted, with the primary objective of understanding the role of the eutopic endometrium in this enigmatic gynecological disorder.