Introduction

Despite the fact that polycystic ovary syndrome (PCOS) is by far the most common endocrine disorder in women, affecting an estimated 5-10% of women of reproductive age, its aetiology and pathogenesis remain uncertain. PCOS usually presents during adolescence and is a heterogeneous syndrome that is classically characterised by features of anovulation (amenorrhoea, oligomenorrhoea, irregular cycles) together with symptoms of androgen excess (hirsutism, acne, alopecia). The most consistent biochemical abnormality is elevation of serum androgen concentrations. Luteinising hormone (LH) concentrations are often also raised, whereas levels of follicle-stimulating hormone (FSH) are normal. It is now well established that PCOS is also characterised by metabolic abnormalities, particularly insulin resistance and hyperinsulinaemia, which are associated with an increased risk of developing type 2 diabetes in later life. It is important to emphasise, however, that the syndrome is by nature heterogeneous and that the spectrum of presentation of PCOS includes women with anovulation who have no symptoms of androgen excess (although most have raised serum androgen concentrations) as well as those with hyperandrogenism but regular menses. The recognition of this heterogeneity underpins the revision of the diagnostic criteria for PCOS that resulted from the joint consensus meeting of the European Society for Human Reproduction and Embryology (ESHRE) and the American Society for Reproductive Medicine (ASRM). Thus the so-called ‘Rotterdam’ diagnostic criteria are defined by the presence of two of the three following features:

1. ∎ polycystic ovaries

2. ∎ anovulation

3. ∎ androgen excess (clinical and/or biochemical).