Hormonal Birth Control Might Cause the Brain's Hypothalamus to Shrink

The research adds to the growing number of studies detailing brain changes in women on the pill.

By Leslie Nemo
Dec 4, 2019 10:00 AM
Birth Control Pill
(Credit: Image Point Fr/Shutterstock)


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Women on birth control pills might have a slightly smaller hypothalamus, a brain region responsible for regulating several kinds of hormones.

That’s according to new research that will be presented today at the Radiological Society of North America's annual meeting. The study, which is still undergoing review and edits in an academic journal, offers a preliminary look at how hormonal birth control pills might change brain structures.

The results don’t necessarily imply that a smaller hypothalamus in these women has negative repercussions, says Michael Lipton, a radiologist at the Albert Einstein College of Medicine and Montefiore Medical Center in New York City, who is discussing the research at the conference.

“It may not represent a risk at all. It may just represent a way we see the effect of how the drug works,” he says.

Side Effects

The hypothalamus, a small region that lies in the center of the brain, regulates all kinds of hormones in the body. Damage to the hypothalamus can cause issues with sex drive, appetite or blood sugar regulation, Lipton says. Though important, the hypothalamus is small and hard to assess just by looking at brain scan images. That might be why research is just recently finding that birth control could impact the region's size, Lipton says. 

The most important ingredients in most oral contraceptives, estrogen and a form of progesterone, are hormones that are active in the brain and trigger changes in reproductive organs to prevent pregnancy. Other researchers have investigated whether individuals taking these extra hormones see physical changes besides not getting pregnant — including changes in the brain. A growing body of evidence indicates that birth control drugs are associated with changes in the size of various brain structures.

Lipton's lab recruited 50 women — 21 of whom said they were on the two-hormone birth control pill — for MRI scans. None of them had been on any other form of hormonal contraceptive before, nor did they have any history of traumatic brain injury or mental illness. When the team looked at overall brain region volume, the hypothalami in women on birth control were about 6 percent smaller than those of other women. Though it’s a small change, even minor alterations can make a big difference in an organ that's as dense as the hypothalamus. “I like to tell people that for all parts of the body, size matters most in the brain,” Lipton says.

So What?

Because this is a preliminary study, more research needs to happen to refine the link between birth control and the hypothalamus. A slightly smaller hypothalamus in these women also doesn’t mean they have any neurological issues, Lipton notes.

Nicole Petersen, a neuroendocrinologist at UCLA and who was not affiliated with the research, says the results agree with other studies on the topic. She herself will be presenting similar research at another conference next week.

But, ultimately, "there is also the eternal question of, 'so what?' " she writes via email. "Assuming this finding is a true finding, what does it mean for a woman whose hypothalamus is made smaller by oral contraceptives?"

There are other, well-documented health risks, like blood clots, women face when going on hormonal birth control. Ultimately, this latest revelation may be just another risk factor that women take into account. “It might one day be part of the conversation when talking with a doctor about birth control,” Lipton says. “But it’s way too soon to tell.”

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