THE combined oral contraceptive pill may reduce the risk of women with polycystic ovary syndrome (PCOS) developing type 2 diabetes, a UK study shows.

Using data from a large UK primary care network database, researchers compared the records of 64,051 women with PCOS against 123,545 controls, and found having PCOS doubled a woman’s risk of developing type 2 diabetes or prediabetes (dysglycaemia).

The findings remained significant across all categories of BMI, the researchers reported in Diabetes Care, highlighting that even normal weight women with PCOS were at increased risk of type 2 diabetes.

The study authors suggested that PCOS-specific factors like androgen excess could be driving increased metabolic risk in women with PCOS, rather than obesity alone.

‘We found that women with PCOS and hirsutism, a clinical feature of androgen excess, had a further increased risk of dysglycaemia,’ they noted.

For the second part of their paper, the University of Birmingham-led research team conducted a nested case-control study of more than 5,000 women with PCOS, half of whom developed dysglycaemia over follow-up.

After adjusting for confounding factors, they found a 27% reduction in the relative risk of developing dysglycaemia among women with PCOS who had used a combined oral contraceptive pill (COCP), with the highest reduction seen in patients receiving the highest numbers of COCP prescriptions.

‘When analysed separately, women with PCOS and COCP use had a similarly reduced risk of dysglycaemia when exposed to COCPs with and without antiandrogenic progestin components, suggesting that the oestrogen-induced increase in SHBG [sex hormone binding globulin] may be the prime-driver of the risk-mitigating effect,’ the study authors wrote.

A large-scale randomised trial was needed to establish a causal effect, with careful comparison of the potential added benefit of COCPs containing antiandrogenic progestin.

‘Though the limitations of our study preclude ascertainment of causality, we hypothesize that a beneficial effect of COCPs might be conveyed by an oestrogen-induced increase in hepatic SHBG production. This increase would result in a decrease in the biologically active, unbound circulating androgen fraction, and this reduction in androgen excess could have metabolically beneficial effects including a decrease in risk of dysglycaemia,’ they wrote.