British scientists have found that a common gene variant that predisposes carriers to obesity is also linked to polycystic ovary syndrome (PCOS). PCOS has long been known to be associated with obesity but the new study is the first to identify a genetic link between the two conditions.

The connection between obesity and PCOS prompted researchers at the Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford and Imperial College London, to investigate whether a gene variant linked to obesity also influenced the likelihood of developing PCOS. They looked at a gene known as the fat mass and obesity gene, or FTO, which has a variant known to be associated with increased body mass index and obesity. More than half of all people of European descent carry one or two copies of this FTO variant and those that have two copies are on average seven pounds heavier and 67 times more likely to be obese than those who don't carry it.

The research team, led by Dr Tom Barber, analysed the FTO gene in 463 women with PCOS and 1,336 women without PCOS to see which variant they carried. They found that women who carry the FTO variant that predisposes them to weight gain are also at greater risk of developing PCOS. They presented this data at the Society for Endocrinology BES meeting in Harrogate.

PCOS affects approximately one in ten British women of reproductive age, and is recognised to be the leading cause of ovarian failure leading to infertility in pre-menopausal women in the UK. Tiny cysts develop in the ovaries of affected women and they frequently fail to produce a mature egg during the monthly menstrual cycle. Symptoms include light, irregular or absent periods, difficulty conceiving, weight gain, acne and excessive bodily hair growth.

Dr Barber said: '[PCOS] is a genetic condition and one that is strongly associated with obesity; it is therefore of huge relevance for women given today's obesity epidemic...Our data provide the first genetic evidence to corroborate the well-documented association between these two conditions'.

Not all women with PCOS are overweight, but Dr Barber believes that obesity and PCOS may be connected by disturbances in the production of hormones such as testosterone and insulin. He added: 'Our future work will focus on elucidating the underlying mechanisms of PCOS and its metabolic consequences with the hope of understanding how this common condition develops'. This knowledge may contribute to the development of better therapies for PCOS.