Polycystic Ovaries

Polycystic ovaries refer to ovaries that appear enlarged on ultrasound and contain an abnormally high number of small, immature follicles (fluid-filled sacs containing developing eggs), typically 12 or more per ovary or 20 or more under newer diagnostic criteria. These follicles develop because hormonal imbalances in PCOS—particularly excess androgens and disrupted LH/FSH signaling—prevent normal egg maturation, causing follicles to accumulate rather than progress through the menstrual cycle to ovulation. Despite the name, these are not true 'cysts' but rather arrested follicles, and having polycystic-appearing ovaries on ultrasound alone does not confirm a PCOS diagnosis—at least two of the three Rotterdam Criteria must be met.