What Causes PCOS? Scientists May Have Finally Found an Answer

Polycystic Ovary Syndrome—the leading cause of infertility in women—could be triggered in the womb, according to scientists who have reversed the little-understood condition in mice. 

Researchers in France believe PCOS could be caused by the fetus being overexposed to a hormone known as anti-Müllerian (AMH). 

PCOS affects as many as five million women of reproductive age in the U.S. Those with the condition have higher than normal levels of male hormones, which can trigger excess hair on the face and body. Other symptoms include multiple cysts on the ovaries, as well as irregular periods and difficulties becoming pregnant.

Scientists at the French National Institute of Health and Medical Research measured levels of the hormone in a cohort of pregnant women with and without PCOS. In the study, published in Nature Medicine, they showed that AMH levels were significantly higher in women with the syndrome. 

As the syndrome can be hereditary, the team investigated whether high levels of AMH during pregnancy could spark the condition in fetuses. The researchers dosed pregnant mice with high levels of AMH, and found it caused them to have symptoms of PCOS including irregular menstruation, fertility issues, and late puberty. They surmised that the excess levels of AMH promoted brain cells in the fetus to produce too much testosterone.

Using the IVF drug cetrorelix, researchers were able to reverse the induced symptoms of PCOS in the mice. By the end of the year, scientists hope to trial cetrorelix on women with PCOS.

Dr. Paolo Giacobini, lead author of the study, told New Scientist: “It [the drug] could be an attractive strategy to restore ovulation and eventually increase the pregnancy rate in these women."

Robert Norman, a professor of periconceptual medicine at the University of Adelaide in Australia, who was not involved in the study, told New Scientist the study presented "a radical new way of thinking about polycystic ovary syndrome and opens up a whole range of opportunities for further investigation." 

Megan M. Stewart, the founder of the PCOS Awareness Association, told Newsweek "the findings are nothing short of astonishing. PCOS Awareness Association shared this article with our followers from around the world and there is a great deal of hope and excitement that future generations will not have to suffer the way 10 million women with PCOS suffer today. We are also eager to help, in any way possible, with any future studies on PCOS."

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