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Everything to Know About a New Study on the Causes of PCOS

If you don’t have polycystic ovary syndrome, the odds are decent that you know somebody who does. In the U.S., an estimated 10 percent of women of childbearing age have have PCOS, a hormonal disorder that interferes with regular ovulation, often causing irregular periods and fertility issues.

For a condition so common, though, PCOS is also pretty mysterious: there’s no test for it, and researchers haven’t yet hit on a definitive reason why some women develop it while others don’t. A study on mice published earlier this week in the journal Nature, though, claimed to bring us one step closer to understanding PCOS, arguing that it’s caused by exposure to high levels of a hormone called anti-Müllerian while in the womb. More importantly, the authors also said they were able to reverse PCOS in their animal subjects by giving them a drug often used during IVF.

Cool! Maybe. According to Lauren Streicher, an associate professor of obstetrics and gynecology at Northwestern and the author of Sex Rx, this probably isn’t the breakthrough headlines are painting it to be. “It’s very preliminary animal research that’s quite interesting, but it’s not necessarily the whole story,” she says. Here’s what you should know about PCOS in general and this new development in particular.

First things first, what exactly is PCOS?
Contrary to what the name implies, some women with PCOS don’t have any ovarian cysts at all. A diagnosis typically comes when a woman has at least two out of three symptoms: cysts on the ovaries, irregular periods, and/or elevated levels of androgen, a type of hormone that can cause acne, hairiness, and male-pattern baldness. While it’s possible to get pregnant with PCOS, the condition is one of the most common causes of infertility; women with PCOS are at also greater risk of insulin resistance and diabetes, as well as obesity.

The exact collection of symptoms will vary from person to person, and many women can go for years without knowing they have it. Unfortunately, there’s no way to test for PCOS besides testing for individual symptoms, like blood work to assess hormone levels or an ultrasound to look for cysts.

Do we know what causes it?
Sort of? According to the National Institutes of Health, researchers believe that genetics play a role, and “environmental factors” probably have some influence as well. Beyond that, though, it’s still pretty murky.

But as Streicher explains, that may be because there just isn’t any one cause. “There are a lot of things that can upset the balance of what’s going on hormonally,” she says. “We wish with all medical conditions that we could have a one-cause, one-effect sort of thing, but that’s just not the nature with most medical conditions. We know there’s a lot of influences with how we work hormonally and how these hormone levels are adjusted, and there are a lot of points along the way that could be a cause of disruption.”

Is there any treatment?
Just like testing for PCOS comes down to testing for individual symptoms, the same is true of treating it. Birth-control pills can help put women back on a regular cycle and regulate some of the hormonal side effects of PCOS, including acne and hair growth, while other drugs can stimulate ovulation to increase the odds of getting pregnant. Lifestyle adjustments, like maintaining a healthy diet and exercising regularly, can also help keep insulin resistance in check.

Okay, so tell me about this new study.
As a first step, the study authors injected pregnant lab mice with anti-Müllerian and then monitored the resulting female baby mice as they grew into adults, observing that most of them had some symptoms of PCOS — they didn’t ovulate regularly, they didn’t get pregnant as easily, and they showed over-stimulation in brain cells responsible for regulating androgen hormones.

Next, they injected the offspring with cetrorelix, a drug used to regulate ovulation in women undergoing IVF — and when they did, those PCOS symptoms went away. Later this year, the researchers told New Scientist, they’re planning to set up a clinical trial to see if cetrorelix can have the same effect in women.

So how should I feel about it?
Right now, probably nothing more than cautiously intrigued, Streicher says, in large part because of the study subjects used. “Mice aren’t people,” she says. “They induced PCOS in these mice, and then they said, ‘Now we’re going to reverse it by doing such-and-such’ — that doesn’t translate to what causes PCOS in humans.”

Plus, there’s that whole thing about multiple causes. Exposure to anti-Müllerian hormone “may be one of the things that causes it,” she says, “but the idea that we’ve found the cause of PCOS, and now we’ve found the cure, is a huge overstatement.” In reality, understanding PCOS may be much more complex — not because we haven’t yet found the single right answer, but because there isn’t one.

Everything to Know About a New Study on the Causes of PCOS