Polycystic ovary syndrome (PCOS) explained

What PCOS actually is

PCOS is a condition where the balance of hormones that control the menstrual cycle is disturbed. In many people with PCOS, the ovaries make slightly more androgens — hormones such as testosterone that everyone has in small amounts — and the ovaries may not release an egg regularly each month. The "polycystic" ovaries seen on a scan are not true cysts but many small, immature egg-containing follicles sitting just under the surface. A key player is insulin resistance, where the body responds less well to insulin; this can drive weight gain and push the ovaries to make more androgens. PCOS is not caused by anything a person did wrong, and it often runs in families.

Recognising the symptoms

PCOS shows itself differently from person to person. Common features include irregular, infrequent, or absent periods, because ovulation happens unpredictably. Higher androgen levels can cause excess hair growth on the face or body (hirsutism), acne, and sometimes thinning of the hair on the scalp. Many people find weight harder to manage, and difficulty getting pregnant is a frequent reason people first seek help, because irregular ovulation makes timing harder. Symptoms often begin in the teenage years but may be mild at first. Importantly, not everyone has every feature, and some people with polycystic-looking ovaries on a scan have no symptoms at all — which is why diagnosis depends on the overall picture rather than any single finding.

How PCOS is diagnosed

In the UK, doctors usually use the Rotterdam criteria, which require at least two of three features: irregular or absent ovulation (often seen as irregular periods), signs of high androgens (either on examination or in blood tests), and polycystic ovaries on an ultrasound scan. Crucially, PCOS is a diagnosis of exclusion — other conditions that cause similar symptoms, such as thyroid disorders, a hormone called prolactin being raised, or rarer adrenal problems, must be ruled out with blood tests first. A pelvic ultrasound is often arranged, though it is not always essential, particularly in younger people where polycystic-appearing ovaries can be normal. Because the label carries long-term health implications, an accurate diagnosis matters, and your GP may involve a specialist.

Why it matters for long-term health

PCOS is not only about periods and fertility; it also affects longer-term health, largely through insulin resistance. People with PCOS have a higher risk of developing type 2 diabetes and, over time, cardiovascular problems, so regular checks of weight, blood pressure, blood sugar, and cholesterol are recommended. If periods are very infrequent, the lining of the womb can build up without regular shedding, which slightly raises the risk of womb (endometrial) changes over many years — so ensuring at least a few bleeds a year is important. PCOS is also linked with a higher chance of mood problems, including anxiety and depression, and with sleep issues. Recognising these connections allows problems to be prevented or caught early through routine monitoring.

Treatment and living well with PCOS

There is no cure for PCOS, but symptoms can be managed well and long-term risks reduced. Lifestyle support is the foundation: even modest weight loss, if appropriate, can restore more regular periods, improve fertility, and lower diabetes risk, and balanced eating with regular activity helps insulin work better. Treatment is tailored to what matters most to each person. Hormonal contraception can regulate periods and improve acne and excess hair; other medicines can help with hair growth, and options exist to help ovulation for those trying to conceive, usually guided by a specialist. Emotional wellbeing deserves attention too. With the right combination of self-care, monitoring, and medical treatment, most people with PCOS lead full, healthy lives.