At the base of the brain is a small but crucial area that acts as a control hub for the nervous and hormonal systems. Now, a study has found that among women, it is significantly smaller in those using birth control pills.

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New research finds an intriguing link between birth control pills and the size of a brain area key for managing the hormonal system.

The Food and Drug Administration (FDA) first approved birth control pills for use in the United States in 1960. Today, in the U.S., 12.6% of women between the ages of 15 and 49 years take these pills.

Known simply as “the pill,” this oral contraceptive is one of the most popular forms of birth control, but people also use it to help with a wide range of conditions, including irregular menstruation, acne, polycystic ovary syndrome, endometriosis, and cramps.

In essence, the pill began as a way of preventing pregnancy using hormone control.

Originally, manufacturers engineered it to stop ovulation through the hormone progesterone, but it has since evolved to include a myriad of different types. These involve various hormone combinations, doses, and schedules, depending on the desired outcome. People can also use the pill to skip menstruation or stop it entirely.

But what does this harnessing of hormone power mean for the body’s natural system of hormones?

Before the current study, which the researchers presented at the 2019 annual meeting of the Radiological Society of North America, there was very little research into the effects of birth control pills on the hypothalamus.

This small region of the brain, which sits above the pituitary gland at the organ’s base, performs the vital role of producing hormones and helping control a range of bodily functions — including sleep cycles, mood, sex drive, appetite, body temperature, and heart rate.

The researchers who presented the study acknowledged that before their work, there had not been any reporting on the effect of birth control pills on the structure of the human hypothalamus.

“There is a lack of research on the effects of oral contraceptives on this small but essential part of the living human brain,” says Michael Lipton, Ph.D., who is a professor of radiology at the Gruss Magnetic Resonance Research Center at Albert Einstein College of Medicine and medical director of MRI Services at the Montefiore Medical Center, both in New York City, NY.

This may be down to the fact that, until now, there was no known way of quantitatively analyzing MRI exams of the hypothalamus.

Lipton explained to Medical News Today that the team’s previous work also inspired them to investigate these effects. “We have reported some quite interesting findings on sex-based risk in brain injury,” he said. “Specifically, women seem to fare worse than men. Other studies have shown that the female sex hormone progesterone is neuroprotective.”

“Since [oral contraceptive pills] are widely used, we wanted to explore the effects of [oral contraceptive pills] in healthy women to understand their potential role in our sex-divergent findings. The finding we report here is one outcome from that exploration.”

“I was not expecting to see such a clear and robust effect,” said Lipton. The researcher also notes, “We found a dramatic difference in the size of the brain structures between women who were taking oral contraceptives and those who were not.”

For the study, the researchers recruited 50 women in good health, 21 of whom were taking birth control pills.

The team carried out MRI scans, which use radiology to generate images of organs, to look at the brain of each of the 50 women. They then used a validated methodology to gauge the hypothalamic volume.

“We validated methods for assessing the volume of the hypothalamus and confirm, for the first time, that current oral contraceptive pill usage is associated with smaller hypothalamic volume,” says Lipton.

The researchers found that the women taking birth control pills had a significantly lower hypothalamus volume than those who were not using oral contraceptives.

Although the study found that there was no noteworthy link between hypothalamic volume and a woman’s cognitive ability, or ability to think, the preliminary findings suggest that there is an association between smaller hypothalamic volume and reduced anger.

“These findings are generally consistent with previous studies of [oral contraceptive pills] that support [an effect] on mood regulation. Our finding might represent a manifestation of the mechanism behind these effects or simply be unrelated. It is just too soon to tell,” said Lipton.

“This initial study shows a strong association and should motivate further investigation into the effects of oral contraceptives on brain structure and their potential impact on brain function,” concludes Lipton.

Regarding plans for future work, Lipton said: “For my group, the most important and immediate goal is to incorporate the role of [oral contraceptive pills] into our ongoing studies and to further explore the role of normal sex hormone cycles related to the menstrual cycle, as well as the role of androgens (testosterone) in men and women.”