['The estradiol-to-testosterone (E2/T) ratio has been investigated in different diseases but few in vivo data are available with regard to its role in women with ovary syndrome (PCOS). The aim of this study was to evaluate the role of the E2/T ratio in the ovulatory function and metabolic pattern in such women.', 'We retrospectively evaluated hyperandrogenemia, clinical hyperandrogenism, ovarian morphology, hypothalamo-hypophyseal axis and metabolic syndrome parameters in a cohort of 202 consecutive women affected by PCOS. An oral glucose tolerance test measured areas under the curve for insulin (AUC(2hIRI)), for glucose (AUC(2hglucose)), and the HOMA-IR and Matsuda index of insulin resistance were evaluated. Serum progesterone (Pg) was determined from day 20 to day 24 of the menstrual cycle and chronic oligo-anovulation was established if two consecutive cycles were anovulatory.', 'Women with PCOS with normal ovulation [66/202 (32.7%)] showed a significantly higher E2/T ratio than women with PCOS with chronic oligo/anovulation [136/202 (67.3%)] (p < 0.05). Using a series of multiple linear regression models, we also investigated which variables correlated with the E2/T ratio. The analysis showed a strongly positive correlation of the E2/T ratio with Pg (β =\u2009 0.473, p < 0.001) and a negative correlation with total cholesterol (β =\u2009 -0.433, p < 0.001).'] Is low estradiol-to-testosterone ratio associated with oligo-anovulatory cycles and atherogenic lipidic pattern in women with polycystic ovary syndrome?