Polycystic ovary syndrome (PCOS)
A common hormonal condition that can affect ovulation, periods, skin and hair, and long-term metabolic health.
Overview
PCOS is one of the most common hormonal conditions in women of reproductive age, affecting around 1 in 10.
In adults it is usually diagnosed when at least two of the following are present, after other causes have been excluded: irregular or absent ovulation; signs of raised androgens (such as excess hair growth or acne) or raised androgen levels on a blood test; and polycystic ovaries on ultrasound or a raised AMH level.
Despite the name, the ovaries do not contain true cysts. The 'cysts' are small follicles that have paused in development.
What is well established
- PCOS is the most common cause of infertility due to irregular or absent ovulation.
- Effective treatments are available to help ovulation, and many people with PCOS conceive.
- For people with a higher BMI, modest weight loss (around 5%) can improve cycle regularity and ovulation.
- PCOS increases the risk of type 2 diabetes and gestational diabetes, so periodic metabolic checks are recommended.
- The 2023 international evidence-based guideline allows a raised AMH level to be used instead of an ultrasound scan in adults.
Uncertain or emerging evidence
- The exact causes of PCOS are not fully understood; genetics, insulin resistance and androgen effects all appear to contribute.
- Evidence for specific diets or supplements (for example inositol) is mixed and generally of low certainty.
When to seek help
Periods that are absent for three months or more, or fewer than eight periods a year, are worth discussing with a doctor.
This guide is general information and does not replace advice about your own circumstances. Clinical review pending.