Objective: To understand the phenotypic presentation of women with polycystic ovary syndrome (PCOS) of different ethnicities and at different ages.

Design: Cross-sectional, retrospective data analysis (1988 - 2009).

Setting: Specialist clinic in a University Hospital, Leicestershire, UK.

Participants: Women with PCOS, n = 1310 (mean age 26·2 years), 70·9% White and 29·1% South Asian (SA) attending a speciality clinic in Leicester UK.

Main outcomes measures: Clinical and demographic characteristics of women with PCOS including age at first clinic appointment, signs and symptoms, body mass index (BMI) and blood pressure (BP).

Results: Compared to White women, the SA were younger (24·3 vs 27·1 years, P < 0·001), less likely to smoke (3·7% vs 17·9% P < 0·001) and had a higher prevalence of acanthosis nigricans (AN) (16·8% vs 3·1% P < 0·001), type 2 diabetes (T2DM) (8·1% vs 5·6%, P < 0·01) and hirsutism (88·5% vs 77·4%, P < 0·001), with lower systolic (126·5 vs 133·0 mmHg, P < 0·001), diastolic BP (71·8 vs 75·1 mmHg P = 0·008) and BMI (29·3 vs 31·5 kg/m(2) P = 0·002). Differences in body weight remained when participants were classified as obese, overweight and normal according to ethnicity-specific cut-off points (P = 0·048). In both ethnicities, those aged ≥30 years old had higher rates of obesity, T2DM, hypertension and infertility, and less acne, and oligomenorrhoea. Obesity was associated with increased T2DM, AN, systolic/diastolic BP, hirsutism and infertility.

Conclusion: The phenotypic and metabolic presentations of women with PCOS appear to be significantly different depending on ethnicity, obesity and age. This has implications for management strategies in these groups.