Testosterone might make teens more likely to catch whipworm—but also help keep the worms under control.

Other research found that among teenagers, higher testosterone levels were tied to a higher chance of being infected with whipworm, but those same teens ended up with fewer worms in their system when they were infected. That’s a surprising twist—like the hormone makes it easier to catch the parasite but also helps the body keep it in check. And this effect didn’t show up at all with roundworm, which suggests the relationship isn’t about testosterone in general, but something specific to how the body responds to whipworm. It’s also worth noting this only applied to teens aged 12 to 19, so we can’t assume the same pattern holds for kids or adults.