The “cysts” in PCO are actually small immature follicles, which, as explained above, are normal features of all ovaries; when large numbers of antral follicles are visible on ultrasound scan (>20 in the most recent guidelines released in 2018) and/or the volume of the ovary is increased, the ovary is considered to be polycystic.
For a diagnosis of PCOS, two out of three of the following criteria need to be present:
- Polycystic appearing ovaries (PCO) on ultrasound.
- Irregular, infrequent or absent periods, which reflect infrequent or absent ovulation (ovulation is the release of an egg from the ovary).
- Increased levels of male hormones or signs of increased male hormone effects, such as excessive body hair growth.