Lean polycystic ovary syndrome (PCOS): an evidence-based practical approach

Polycystic ovary syndrome (PCOS) is a common endocrinopathy affecting women of reproductive age. Common features include menstrual irregularities, hyperandrogenism and polycystic ovarian morphology although the presentation can be heterogeneous. Insulin resistance is thought to be responsible for the hormonal and metabolic derangements observed. PCOS has two phenotypes, overweight/obese and lean, the latter being a much less common presentation of the syndrome.

The aim of the present review is to summarise cardinal features, and to devise diagnostic and treatment algorithms for lean PCOS based on recent literature.

We searched PubMed, EBSCOhost and Google Scholar using search terms such as 'lean polycystic ovary syndrome' OR 'lean polycystic ovarian syndrome' OR 'lean PCOS' OR 'lean polycystic ovary disease' OR 'lean polycystic ovarian disease' OR 'lean PCOD' OR 'hyperandrogenism' AND 'low BMI OR 'low body mass index' to identify potential articles to be included in the review. Citation searches were subsequently performed in order to find relevant literature.

Hormonal, metabolic and haematological profiles were altered in lean women with PCOS compared to healthy counterparts. However, the derangements were either comparable or less obvious compared to obese women with the syndrome. Insulin resistance seemed inherent in PCOS independent of obesity. Treatment options included weight maintenance, restoration of ovulation with insulin-sensitizers such as metformin, relief of symptoms such as hirsutism, acne and menstrual dysfunction, and assisted reproductive technologies in refractory cases, all of which showed promising results. The literature with evidence on lean PCOS is of low to moderate quality and there are still some uncertainties in the evidence base.

Carefully designed randomised controlled trials are required to confirm findings of previous studies in lean PCOS and to consolidate diagnostic and management algorithms proposed in this review. This paper will aid health professionals to improve their clinical approach in managing lean women with PCOS.