What is PCOS?

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PCOS is a syndrome where at least two of the following occur, and often all three:

At least 12 follicles (tiny cysts) develop in your ovaries. (Polycystic means 'many cysts'.)
You do not ovulate each month. Some women with PCOS do not ovulate at all. (In PCOS, although the ovaries usually have many follicles, they do not develop fully and so ovulation often does not occur.) If you do not ovulate then you do not have a period.
The balance of hormones that you make in the ovaries is altered. In particular, your ovaries make more testosterone (male hormone) than normal.

How common is PCOS?

PCOS is common. Research studies of women who had an ultrasound scan of their ovaries found that up to 1 in 5 young women have polycystic ovaries (ovaries with many small cysts). However, many of these women were healthy, ovulated normally, and did not have high levels of male hormones. It is thought that up to 1 in 10 women have polycystic ovary syndrome (PCOS) - that is, at least two of: polycystic ovaries, a raised level of male hormone, reduced ovulation.