Before delving into your off-the-charts sex drive, a little biology lesson: “A female menstrual cycle involves the cyclical rise and fall of estrogen, progesterone, testosterone, and DHEA,” says Adeeti Gupta, M.D., an ob-gyn and founder of Walk In GYN Care.

All these hormones play an important role in your sex drive. While we know there’s a link, scientists aren’t totally sure how your cycle impacts your sex drive.

In a study published in Hormones and Behavior, researchers explored the connection in a group of undergraduate women. They measured hormone levels over two full menstrual cycles, and compared the results to daily journals where the participants recorded sexual activity and feelings of friskiness.

The researchers found that changing levels of estrogen and progesterone had serious sex drive side effects. Likely because, “estrogen promotes libido and desire,” explains Gupta. “Progesterone is a stabilizing hormone that suppresses libido.”

Before that time of the month, all those hormones reach a heightened state. But right before your period, they crash, says Nan Wise, Ph.D., a cognitive neuroscientist and certified sex therapist. “During week one of your period, when you're bleeding, estrogen starts a steady climb,” she says.

This moment during your cycle can be particularly ripe for gotta-have-it-now desire. “During and right after the period is when progesterone”-the hormone that suppresses your sex drive-"is the lowest,” explains Gupta. Meanwhile, your desire-boosting estrogen levels are building up, making a case for increased horniness.

That said, based on hormones alone, your period probably isn’t the peak of your sexual desire. Research shows that your fluctuating hormone levels prime you to be the horniest around ovulation-about half-way through your cycle or two weeks after your period.

That means there could be other factors playing into your friskier-than-normal feelings during your period, says Wise.

“Some women report that if they masturbate or have sex, the sense of the pelvic congestion or the menstrual cramps is relieved,” she explains. Sex and orgasm can decrease stress and help ease any PMS pain-two things you might be subconsciously craving during that time of the month.

Feeling horny during your period may also just come down to individual differences, says Wise. “Women might like sex more or a whole lot less in that period of time depending on their physical comfort,” she says. For some women, when they’re bleeding and crampy, the last thing they want is sex-however, some women want sexual activity for relief.”

The bottom line: If you don’t feel particularly horny during your period, don’t worry-nothing is off. But if you do suddenly feel sex-crazed, the most likely culprit is your naturally shifting hormone levels. Feel free to send your ovaries a thank you card.