['To investigate intrinsic alterations in ovarian steroidogenesis in women with clomiphene citrate (CC)-resistant polycystic ovary syndrome (PCOS) who ovulated after metformin treatment.', 'Fifty-six women of reproductive age (18-40 years) diagnosed with CC-resistant PCOS received metformin for 12 weeks. If ovulation was successfully induced by CC after metformin treatment, the women were classified as responders. Circulating levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2), testosterone (T), free testosterone (freeT), fasting insulin and sex hormone-binding globulin (SHBG) were determined at weeks 0, 4 and 12 of metformin treatment.', 'Thirty-seven women with CC-resistant PCOS finished the treatment course. There were no significant differences in circulating levels of FSH, E2, T, freeT and fasting insulin at weeks 0, 4, and 12 between responders and nonresponders. At week 4, responders showed significantly higher LH levels and higher LH/FSH ratios than non-responders (p < 0.005 and p < 0.05, respectively). After the 12-week treatment, responders demonstrated higher serum E2/T ratios and lower freeT levels than non-responders (p < 0.05 and p < 0.05, respectively).'] Is estradiol-to-testosterone ratio associated with response to metformin treatment in women with clomiphene citrate-resistant polycystic ovary syndrome ( PCOS )?