Women with polycystic ovary syndrome (PCOS) are four times more likely than women without the condition to develop type 2 diabetes and to be diagnosed at an earlier age, according to a large study in Denmark.
Researchers followed about 80,000 women for an average of 11 years to see if higher rates of insulin resistance and obesity that tend to go along with PCOS translated to higher risk of diabetes.
Women with PCOS often have small painless cysts in the ovaries as well as high levels of testosterone and other hormones that can cause irregular or absent menstrual periods, infertility, weight gain, acne or excess hair on the face and body.
The condition is the most common hormonal disorder in women of childbearing age, affecting some 5 to 6 million women in the US, according to the Endocrine Society.
"We confirm that the risk for diabetes is increased in PCOS - but we need more knowledge about risk factors such as weight," study author Dr. Dorte Glintborg of Odense University Hospital told Reuters Health by email.
The researchers analysed data from the Danish National Patient Register for more than 18,000 women with PCOS along with about 1,100 women with PCOS who were patients at the Odense University Hospital.
For each woman diagnosed with PCOS, researchers also selected three women born in the same year who did not have either diabetes or PCOS to form a comparison group.
At the end of the follow-up period, the rate of new cases of type 2 diabetes among women with PCOS was 8 per 1,000 women per year. In comparison, 2 women per 1,000 without PCOS developed diabetes each year.
Women with PCOS were diagnosed with type 2 diabetes at an average age of 31, while the average age at diagnosis without PCOS was 35, the study team reports in the Journal of Clinical Endocrinology and Metabolism.
Having a high body-mass index (BMI), a measure of weight relative to height, as well as high insulin, blood glucose and triglycerides were all associated with higher risk for type 2 diabetes. Giving birth was tied to lower risk.
Women with PCOS should work with their general practitioner and do follow-up screening if they're obese, Glintborg said. They should also exercise and keep a healthy lifestyle, she added.
"It's the first nationwide prospective study looking at the development of type 2 diabetes in women with PCOS," said Dr. Melissa Sum, an endocrinologist at New York University Langone Health in New York City who wasn't involved in the study.
"It was well done in that it had a large cohort of women and they were followed before they got the diagnosis of diabetes," she said in a phone interview.
The main finding of a higher rate of type 2 diabetes is consistent with previous studies, Sum added, noting the significance of the age difference at diagnosis between women with versus without PCOS.
"It's important for women with PCOS to know they are at risk for type 2 diabetes and gestational diabetes, even at younger ages," she said.
Sum thinks the association of a high BMI with type 2 diabetes is important because it's a modifiable risk factor.
"Women could talk to their physician earlier on for counseling and also to get a good tune up regarding whether their overall health and their BMI are appropriate or whether they can do anything for risk factor modification in terms of future development of diabetes," she said.