A 28-year-old patient complained about prolongation of intermenstrual periods up to 2 months, hirsutism. Gynaecological examination revealed that the ovaries were enlarged, painless, compact, uterus had no pecularities. Pelvic ultrasound revealed that the ovaries were 4-5 cm in diameter and had multiple enlarged follicles on periphery. Roentgenography of skull base showed that sellar region was dilated. What is the most probable diagnosis?