Association between Type 2 diabetes mellitus and polycystic ovary syndrome (PCOS)

• Prospective studies provide evidence that the prevalence of both Type 2 diabetes mellitus and impaired glucose tolerance is higher in women with PCOS than in age- and weight-matched women without PCOS.
• There is evidence from a non-systematic review and small case-control and cross-sectional studies that women with PCOS are more likely to have insulin resistance, and that this is more marked if the woman is obese.
• Good evidence from prospective cohort studies indicates that women with PCOS have an increased risk of developing Type 2 diabetes or impaired glucose tolerance in middle age. Obesity increases the risk of impaired glucose tolerance and diabetes [Legro, 2001].
• Limited evidence from a prospective study indicates that women who have had gestational diabetes mellitus are more likely to have PCOS.

Screening

• These recommendations are based on expert advice from the Royal College of Obstetricians and Gynaecologists [RCOG, 2007], a position statement from the Androgen Excess Society [Salley et al, 2007], and the opinion of CKS expert reviewers.
• It is not known whether or how often women with PCOS should be screened for impaired glucose tolerance or Type 2 diabetes.
• Three cohort studies provide evidence that fasting glucose levels alone are a poor predictor of impaired glucose tolerance and that a family history of diabetes in a first-degree relative may be significant. The evidence suggests that if a test is done, an oral glucose tolerance test is the most appropriate. However this is not always practical in primary care.
• The Royal College of Obstetricians and Gynaecologists suggest an approach to screening that does not involve performing an oral glucose tolerance test on all women with PCOS; it recommends regular (perhaps annual) fasting glucose tests in all women with PCOS but performing an oral glucose tolerance test in women who have a body mass index (BMI) greater than 30 kg/m², a strong family history of Type 2 diabetes, or a fasting glucose level of 5.6 mmol/L or greater [RCOG, 2007].
• The International Diabetes Federation suggests that if the fasting glucose level is greater than 5.6 mmol/L, an oral glucose tolerance test should be done [International Diabetes Federation, 2005].
• A position statement from the Androgen Excess Society suggests that all women with PCOS should have an oral glucose tolerance test. Most members of the Androgen Excess Society Board suggest screening all women with PCOS at least every 2 years with an oral glucose tolerance test, or more frequently if additional risk factors are present. Women with impaired glucose tolerance should be screened annually for Type 2 diabetes. A few members of the Board suggested an oral glucose tolerance test only in women with a BMI of 30 kg/m² or in lean women with additional risk factors [Salley et al, 2007].
• Taking into account the practicalities of screening in primary care, these recommendations are based on:
• The position statement from the Androgen Excess Society that all women with PCOS should have an oral glucose tolerance test [Salley et al, 2007] and the opinion from some CKS expert reviewers that all women with PCOS should have an initial oral glucose tolerance test.
• The position statement from the Androgen Excess Society that all women with impaired glucose tolerance should be screened annually for Type 2 diabetes mellitus [Salley et al, 2007].
• The pragmatic recommendation from the Royal College of Obstetricians and Gynaecologists [RCOG, 2007], and also from some CKS expert reviewers, of annual fasting glucose measurement for all women with PCOS.
• The suggestion from the Androgen Excess Society of doing oral glucose tolerance tests more frequently than once every 2 years in women at particular risk of Type 2 diabetes [Salley et al, 2007].
• CKS has also recommended considering women who have had gestational diabetes mellitus or Asian women with a BMI greater than 25 kg/m² to be at particular risk of Type 2 diabetes; CKS expert reviewers agreed with this suggestion.