ABSTRACT
Polycystic ovary syndrome (PCOS) is a common endocrinopathy, characterized by oligo/anovulation and elevated circulating androgens or evidence of hyperandrogenism, after all known potential causes have been excluded. In addition, insulin resistance and accompanying hyperinsulinemia commonly occur in women with PCOS. There is increasing evidence that the endocrinological and metabolic abnormalities in PCOS may have complex effects on the endometrium, contributing to infertility and endometrial disorders observed in women with this syndrome. Androgen receptors and steroid receptor coactivators are overexpressed in the endometrium of women with PCOS. Also, biomarkers of endometrial receptivity to embryonic implantation, such as αvβ3 integrin and glycodelin, are decreased, and epithelial expression of ERα abnormally persists in the window of implantation in endometrium in women with PCOS. In addition to being responsive to the steroid hormones estradiol, progesterone, and androgens, the endometrium is also a target for insulin, whose receptor is cyclically regulated in normo-ovulatory women. In vitro, insulin inhibits the normal process of endometrial stromal differentiation (decidualization). In addition, insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) are regulated in and act on endometrial cellular constituents, and hyperinsulinemia down-regulates hepatic IGFBP-1, resulting in elevated free IGF-I in the circulation. Thus, elevated estrogen (without the opposing effects of progesterone in the absence of ovulation), hyperinsulinemia, elevated free IGF-I and androgens, and obesity probably contribute to endometrial dysfunction, infertility, increased miscarriage rate, endometrial hyperplasia, and endometrial cancer common in women with PCOS. The potential mechanisms underlying these disorders, specifically in women with PCOS, are complex and await additional transdisciplinary research for their complete elucidation.
