Researchers have linked a hormone used in some birth controls to benign brain tumors, but experts say it's not a reason to drop your pill

• Cyproterone acetate is a hormone drug used to treat acne, early puberty, and heavy periods.
• A study of 253,777 females in France found a link between the hormone and benign brain tumors.
• The hormone is used in birth control, but experts say the dosage is so low there's no need to worry.

A new study suggests a certain hormone drug could increase the risk of developing a noncancerous brain tumor.

The drug, cyproterone acetate, is prescribed to treat acne, early puberty, heavy periods, excessive hair growth, and inoperable prostate cancer.

It is also used in small doses (around 2 mg) in some forms of birth control, such as Diane-35, a contraceptive which was temporarily banned in France in 2013 over claims that it increased the risk of life-threatening blood clots.

In the new study, French researchers analyzed data on 253,777 females aged seven to 70 years old who used the drug over a long period of time - anywhere between five and 30 years.

The study found that women who had a higher dosage of cyproterone acetate (more than 3 g) had a seven-fold increased risk of developing noncancerous brain tumors, compared to those with a lower dosage.

Dr. Alexander Khalessi, chair of neurological surgery at UC San Diego Health, wasn't surprised by these findings, given that previous research has established a link between high levels of estrogen and progesterone and benign tumors.

But he said this link isn't something to panic about because the chances of developing a brain tumor are still very low.

"The last thing I want are women across the country suddenly stopping their birth control out of fear of a brain tumor," he said.

Those who take drugs containing cyproterone acetate for more than 3 years should be informed of the risks, experts say

The researchers found that the group of 139,222 people who had a higher dosage of the drug had 69 cases of noncancerous brain tumors, compared to 20 cases in the group of 114,555 people with a lower dosage.

Notably, the risk of developing a noncancerous brain tumor decreased as the hormone treatment stopped.

One limitation of the study is that it was observational, as opposed a randomized clinical trial, which is the "gold standard" of studies - meaning the researchers observed outcomes rather than controlled the experiment.

The researchers say doctors whose patients are taking a high dose of cyproterone acetate over three to five years should have a frank conversation with their patients about the potential link to benign brain tumors, however remote the risk.

That's especially key if a patient has a history or risk of brain tumors, Khalessi said.