Polycystic ovary syndrome - PCOS - affects approximately 1 in 10 women of reproductive age, making it one of the most common hormonal conditions in women. It is also one of the most misunderstood, partly because of its name (which is misleading), partly because its presentation varies enormously between women, and partly because it receives far less research attention and public awareness than its prevalence warrants.
The name is the first problem. Despite what it suggests, you do not need to have polycystic ovaries on an ultrasound to have PCOS. Many women with polycystic-appearing ovaries on scan do not have the syndrome. And the condition involves far more than the ovaries - it is a systemic hormonal and metabolic disorder affecting metabolism, skin, hair, mood, and cardiovascular risk, in addition to the reproductive system.
Why insulin resistance is central to PCOS
The most important concept for understanding PCOS - and for treating it effectively - is insulin resistance.
In insulin resistance, the body produces insulin normally but cells do not respond to it efficiently. The pancreas compensates by producing more insulin. Chronically elevated insulin levels then stimulate the ovaries and adrenal glands to produce more androgens (testosterone, DHEAS). Elevated androgens disrupt ovulation, cause the skin and hair changes of PCOS, and drive a cycle that perpetuates itself.
This is why dietary interventions that reduce insulin levels - particularly reducing refined carbohydrates and sugar - are often significantly effective at improving PCOS symptoms. And it is why metformin, an insulin-sensitising medication, is used in PCOS management even in women without diabetes.
Diagnosis - the Rotterdam criteria
PCOS is diagnosed when at least two of the following three features are present, after other causes of these features have been excluded:
1. Irregular or absent periods: Fewer than 8 menstrual cycles per year, cycles lasting more than 35 days, or absent periods. This reflects infrequent or absent ovulation.
2. Elevated androgens: Either measured in blood (elevated total testosterone, DHEAS, or free androgen index) or evidenced clinically by symptoms including acne, excessive hair growth (hirsutism), or male-pattern hair thinning.
3. Polycystic-appearing ovaries on ultrasound: 20 or more follicles per ovary, or ovarian volume above 10mL on either ovary.
Before diagnosing PCOS, other conditions that can cause similar features must be excluded: thyroid dysfunction, elevated prolactin, congenital adrenal hyperplasia, and androgen-secreting tumours (rare but important to exclude).
Symptoms - the range is wider than most people know
The challenge with PCOS is that no two presentations are identical. Women with PCOS may have some, all, or very few of the following:
Menstrual irregularity: The most common presenting symptom. Periods may be infrequent, absent, or unpredictable. Some women have regular periods despite having PCOS - particularly if their androgen elevation is mild.
Excess hair growth (hirsutism): Hair in a male distribution - upper lip, chin, cheeks, chest, abdomen, lower back, inner thighs. Affects approximately 70% of women with elevated androgens. The degree varies with genetics - women from certain ethnic backgrounds (including South Asian) tend to show more hirsutism at lower androgen levels, while women of African origin may show less visible hirsutism despite significant androgen elevation (due to differences in hair texture and follicle sensitivity).
Acne: Hormonal acne, characteristically affecting the jawline, chin, and lower cheeks rather than the T-zone. Often persists into adulthood or begins in adulthood.
Hair loss: Diffuse thinning at the crown or temples in a male distribution. Can be distressing and significantly affects quality of life.
Weight and weight gain: Many but not all women with PCOS carry excess weight, particularly centrally. However, lean PCOS - PCOS in women of normal weight - is common and often overlooked. Lean women with PCOS may have a normal BMI but still have insulin resistance and all associated features.
Fertility: PCOS is the most common cause of ovulatory infertility. Without regular ovulation, natural conception is more difficult but not impossible.
Metabolic consequences: Women with PCOS have significantly higher rates of type 2 diabetes, metabolic syndrome, and cardiovascular risk. The lifetime risk of type 2 diabetes is approximately 4-7 times higher in women with PCOS than in women without.
Mental health: Anxiety and depression are significantly more common in women with PCOS than in the general population - approximately twice as common. Both the direct hormonal effects and the significant psychosocial impact of symptoms (acne, hair growth, weight, fertility) contribute.
PCOS in women of African heritage
PCOS affects women across all ethnicities but the presentation and associated risks differ. Women of African origin with PCOS tend to have higher rates of insulin resistance, more severe metabolic features, and higher rates of type 2 diabetes risk compared to white women with PCOS - similar to the pattern seen with diabetes risk generally in Black populations. Hirsutism may be less clinically apparent in women with darker skin and coarser hair, potentially leading to underdiagnosis or underestimation of androgen excess in clinical assessment.
Treatment - tailored to what you actually need
Because PCOS affects different women differently, treatment is symptom-directed. There is no one-size-fits-all approach.
For irregular periods and contraception: The combined oral contraceptive pill (COCP) is the most commonly prescribed first-line treatment. It regulates periods, reduces androgen levels (improving acne and hirsutism), and provides contraception. Dianette (co-cyprindiol) is specifically licensed for moderate to severe acne and hirsutism in women who also require contraception. The Mirena coil provides progestogen-only endometrial protection for women who cannot use oestrogen-containing contraceptives.
For hirsutism and acne: Topical treatments (eflornithine cream slows facial hair growth). Spironolactone (an anti-androgen, used off-label in the UK) is effective for both hirsutism and acne when combined with reliable contraception. Laser hair removal provides permanent reduction for established hair growth.
For fertility: Letrozole (an aromatase inhibitor) is now the recommended first-line ovulation induction agent, having superseded clomifene. Metformin improves ovulation rates in insulin-resistant women. Laparoscopic ovarian drilling (LOD) is a surgical option. IVF is available when other approaches fail, though women with PCOS are at higher risk of ovarian hyperstimulation syndrome (OHSS) and require careful protocol management.
For metabolic health: Metformin improves insulin sensitivity and is often prescribed for PCOS even without diabetes, particularly in women with insulin resistance, irregular periods, or difficulty conceiving. It is safe for long-term use. Weight loss of 5-10% of body weight in overweight women with PCOS significantly improves hormonal profiles, menstrual regularity, and fertility - independently of any medication.
Diet: A low glycaemic index (low-GI) diet reduces insulin spikes and is consistently beneficial in PCOS. This does not mean eliminating carbohydrates - it means choosing slower-releasing carbohydrates (oats, legumes, sweet potato, wholegrain bread) over faster ones (white bread, white rice, sugary drinks, processed foods).
Sources: NICE Clinical Guideline CG156 - Fertility Problems (2013, updated 2023); Rotterdam ESHRE/ASRM-Sponsored PCOS Workshop Group 2004; Teede HJ et al, Human Reproduction 2018 (international PCOS guidelines); Balen AH et al, Human Fertility 2016; Patel S, Journal of Human Reproductive Sciences 2018 (PCOS in women of African descent); Legro RS et al, NEJM 2007 (letrozole vs clomifene for ovulation induction).
