Uterine Function: From Normal to Polycystic Ovarian Syndrome Alterations

Background: The endometrium is one of the most important female reproductive organs. Polycystic ovarian syndrome (PCOS) is a reproductive and endocrine pathology that affect women of reproductive age. PCOS negatively affects the endometrium, leading to implantation failure and proliferative aberrations. Methods: We conducted a search at the http://www.ncbi.nlm.nhi.gov/pubmed/electronic database using the following key words: endometrial steroid receptors, endometrium, uterine function, endometrium and PCOS, implantation window, implantation and PCOS, implantation markers, inflammation, oxidative stress. We selected the articles based on their titles and abstracts, then we analyzed the full text and classified the articles depending on the information provided according to the sections of the present review. Results: The endocrine and metabolic abnormalities displayed in women with PCOS promote complex effects on the endometrium, leading to a low rate of implantation and even infertility. Women with PCOS show alterations in the Hypothalamic-Pituitary-Ovarian axis, which results in constant circulating levels of estrogen, similar to those at the early follicular phase, and a deficiency in the withdrawal of estrogen and progesterone. Besides this deficiency in the withdrawal of estrogen and progesterone, the insulin/glucose pathway, adhesion molecules, cytokines and the inflammatory cascade, together with the establishment of a pro-oxidative status, lead to an imbalance in the uterine function, which in turn leads to implantation failure or even endometrial cancer. Conclusion: Women with PCOS display a dysregulation of the Hypothalamic-Pituitary-Ovarian axis, which alters the steroid pathway. In addition, the deficiency in the withdrawal of estrogen and progesterone in the endometrium results in abnormal endometrial cellular proliferation. The imbalance in adipose tissue observed in PCOS patients reinforces the increase in circulating hormones. The present review describes the role of hormones, metabolites, cytokines, adhesion molecules and the insulin/glucose pathway related to the uterine endometrium in women with PCOS and their role in implantation failure and development of endometrial cancer.