Polycystic ovary syndrome (PCOS) is the most common hormonal condition affecting women of reproductive age in the UK, estimated to affect 1 in 10 women. Despite its name, PCOS does not mean a woman has cysts on her ovaries — rather, it describes a hormonal imbalance involving the ovaries that affects ovulation, androgen levels, and metabolic health. PCOS is a leading cause of irregular periods and fertility problems, but it is manageable with the right approach.
What Is PCOS?
PCOS is a hormonal disorder characterised by a combination of features: irregular or absent ovulation (and therefore irregular or absent periods), elevated androgens (male hormones such as testosterone) causing symptoms such as excess hair growth, acne, and scalp hair thinning, and multiple small follicles visible on the ovaries on ultrasound scan (the “polycystic ovary” appearance). The name is misleading — these follicles are not true cysts, and many women with PCOS do not have the ultrasound appearance. A diagnosis of PCOS is made when at least two of these three features are present (the Rotterdam criteria).
PCOS Symptoms
PCOS presents with a wide range of symptoms that vary in severity. Common symptoms include irregular, infrequent, or absent periods (oligomenorrhoea or amenorrhoea), difficulty getting pregnant (subfertility) due to irregular ovulation, excess hair growth on the face, chest, back, and abdomen (hirsutism) — affecting around 70% of women with PCOS, acne and oily skin, thinning hair or hair loss on the scalp (androgenic alopecia), weight gain — particularly around the abdomen — and difficulty losing weight, and darkening of the skin in body creases (acanthosis nigricans, associated with insulin resistance). Many women with PCOS are also diagnosed with anxiety or depression, which occur at higher rates than in the general population.
What Causes PCOS?
The exact cause of PCOS is not fully understood but involves a complex interplay of genetic and environmental factors. Key mechanisms include insulin resistance — around 70% of women with PCOS have some degree of insulin resistance, even at a healthy weight. Excess insulin stimulates the ovaries to produce more androgens and disrupts normal follicle development. Elevated androgen levels disrupt the menstrual cycle and cause the characteristic symptoms of hirsutism and acne. PCOS runs in families, suggesting a strong genetic component — having a mother or sister with PCOS roughly doubles your risk. Obesity worsens insulin resistance and can exacerbate PCOS symptoms, though PCOS also occurs in women of normal or low weight.
Diagnosing PCOS
Diagnosis is based on symptoms, blood tests, and ultrasound scan. Blood tests measure LH, FSH, testosterone, SHBG (sex hormone-binding globulin), and sometimes DHEAS and androstenedione. Fasting glucose and insulin are measured to assess insulin resistance. An AMH (anti-Müllerian hormone) test reflects ovarian reserve and follicle number. Pelvic ultrasound may show the polycystic ovary appearance (12 or more follicles per ovary measuring 2–9mm, or total ovarian volume above 10ml) — though the absence of this does not exclude PCOS. Other conditions that can mimic PCOS — including thyroid disease, hyperprolactinaemia, congenital adrenal hyperplasia, and Cushing’s syndrome — should be excluded.
Long-Term Health Risks of PCOS
PCOS is associated with several important long-term health risks. Women with PCOS have a significantly increased risk of developing type 2 diabetes — up to 5–10 times the risk of women without PCOS — due to underlying insulin resistance. Cardiovascular disease risk is increased. Women who have prolonged absent or very irregular periods are at increased risk of endometrial hyperplasia and endometrial cancer (due to unopposed oestrogen stimulation of the uterus) — this is why women with PCOS who have fewer than four periods per year should take progestogen or the combined pill to induce regular withdrawal bleeds. Mental health conditions including anxiety and depression are significantly more common in women with PCOS. Sleep apnoea affects up to 30% of women with PCOS.
PCOS and Fertility
PCOS is a leading cause of anovulatory infertility (failure to ovulate). However, the majority of women with PCOS who want to conceive are able to do so with appropriate treatment. First-line fertility treatment is ovulation induction — stimulating the ovaries to ovulate. Letrozole (an aromatase inhibitor) is now NICE’s preferred first-line treatment for ovulation induction in PCOS, having been shown to be superior to clomifene (which had been first-line for many years). Metformin is used alongside ovulation induction in some women. If ovulation induction fails, gonadotrophin injections or in vitro fertilisation (IVF) may be recommended. Weight loss in women with PCOS who are overweight can significantly improve the chances of spontaneous ovulation.
NHS Treatment for PCOS Symptoms
Treatment targets specific symptoms as PCOS cannot be cured. For irregular periods and contraception, the combined oral contraceptive pill regulates periods and reduces androgen levels, improving acne and hirsutism. For hirsutism, co-cyprindiol (Dianette) — a pill combining oestrogen and the antiandrogen cyproterone acetate — is effective. Eflornithine cream (Vaniqa) slows facial hair growth. For acne, topical and oral treatments used in the general population are effective. Spironolactone is used off-label as an antiandrogen in some women. Metformin, an insulin-sensitising medication used in diabetes, is used in PCOS to improve insulin resistance, regulate periods, and support weight management — it is not licensed for PCOS but is widely used off-label on NHS guidance.
Lifestyle and PCOS
Lifestyle modification is the first-line treatment recommended by NICE for PCOS in women who are overweight. Even modest weight loss of 5–10% of body weight can restore regular ovulation, improve insulin resistance, reduce androgen levels, and significantly improve symptoms. A diet that manages blood sugar — lower in refined carbohydrates, higher in protein and fibre — is particularly beneficial in PCOS due to the underlying insulin resistance. Regular aerobic and resistance exercise improves insulin sensitivity and supports weight management. Inositol supplements (myo-inositol and D-chiro-inositol) have growing evidence for improving insulin resistance and ovarian function in PCOS, though they are not yet routinely recommended on the NHS.
Important: PCOS is a complex condition with wide-ranging effects on health and wellbeing. If you think you may have PCOS, speak to your GP. An accurate diagnosis and tailored management plan can make a significant difference to your health, fertility, and quality of life.
Related Health Guides on YourHealthXpert
Explore these related NHS-aligned health guides:
- Type 2 Diabetes — PCOS significantly increases risk of developing type 2 diabetes; HbA1c screening is recommended
- High Cholesterol — dyslipidaemia is common in PCOS; cardiovascular risk monitoring is essential
- Anxiety and Depression — mental health conditions are significantly more common in women with PCOS
- Endometriosis — another common gynaecological condition that can coexist with PCOS
- Weight Loss Injections — GLP-1 agonists and inositol are beneficial for metabolic management of PCOS
- Menopause — women with PCOS may experience a delayed menopause