compound added to your toothpaste to protect your pearly whites might have a dark side. The antibacterial agent triclosan, which reduces plaque and your risk of gingivitis, may also wreak havoc on your hormones and affect other bodily functions.

Triclosan’s been approved by the FDA since 1997 as part of Colgate Total toothpaste, but information recently released by the agency raises questions about the research used to prove its safety, according to a Bloomberg report. Some of those studies linked triclosan to malformation of mice bones—and scientists back then may not have been aware of what that could really mean for your hormones.

“You can look at those results and realize, ‘Oh wait a minute, they’re also showing indications of endocrine disruption’,” says Caren Helbing, Ph.D., a professor of biochemistry and microbiology at the University of Victoria.  “At that time, they weren’t really thinking of it as a possibility.”

Research that adds to the concerns has continued to emerge since the product’s approval. A recent University of Michigan study suggests that exposure to triclosan may be related to altered thyroid hormone levels in teens. This is supported by previous animal studies: Helbing found similar disrupted thyroid hormone function in bullfrogs when they were exposed to the human equivalent of 1/10 the amount in a pea-sized toothpaste dollop.

And you don’t want to mess with your thyroid hormones—they’re important to virtually every part of your body, says Helbing. They’re needed for proper brain development, brain function, metabolism, and heart health.

UC Davis researchers also discovered that triclosan hinders muscle function and grip strength in mice. Other animal studies linked the compound to fertility problems and increased allergic responses.

More research is needed on people to confirm what all these animal studies have found.  To help bridge that gap, the EPA began a comprehensive re-evaluation of the chemical’s safety last year, 10 years earlier than it originally planned.

But if you don’t want to take any chances on your chompers in the meantime, pick a toothpaste with stannous fluoride for similar teeth-protecting benefits. A 2014 review in International Journal of Dental Hygiene concluded that any differences between brushing with that and triclosan were likely insignificant.