Women's Brain Structure Changes During Menstrual Cycle [Study]

Many women admit to having mood swings during their menstrual cycle. It may be understandable due to the hormonal changes during their period. A new study suggests that the menstrual cycle doesn't only affect women's reproductive anatomy but also their brain structure.

Menstrual Cycle Affects Brain Structure

Researchers led by Elizabeth Rizor and Viktoriya Babenko from the University of California, Santa Barbara, followed 30 menstruating women throughout their cycles and meticulously documented the anatomical alterations in the brain when hormone profiles vary. Previous studies on the hormonal effect on the brain focused on brain communication during cognitive tasks, not the structures themselves.

The new study, which has not yet been subjected to peer review but is available on the preprint server bioRxiv, indicates that structural alterations in the brain during menstruation may not be restricted to areas connected to the menstrual cycle. It has been discovered that hormonal changes, such as puberty, oral contraceptives, gender-affirming hormone therapy, and post-menopausal estrogen therapy, alter the microstructure of white matter, the fatty network of neuronal fibers that transmit information across regions of gray matter.

To close the menstruation gap, the team performed MRI images on their individuals during three menstrual stages: menses, ovulation, and mid-luteal. The researchers also measured the subjects' hormone levels at the time of each of these scans.

The findings demonstrated that as hormone levels fluctuate, so do the quantities of gray and white matter and cerebrospinal fluid. In particular, the subjects' brains displayed white matter alterations that suggested quicker information transfer soon before ovulation, when the hormones 17-estradiol and luteinizing hormone surge.

The ovary follicle-stimulating hormone, which rises before ovulation and aids in activating them, was linked to thicker gray matter. After ovulation, progesterone levels rise and are linked to increased tissue and decreased cerebrospinal fluid volume.

Although it is unclear what this means for the person operating the brain, the study lays the framework for further research. It could help us understand the reasons for severe but unique mental health issues associated with periods.

Pregnancy Hormones Change Women Permanently

Another study previously revealed that the hormones from pregnancy change moms forever. Pregnancy hormones flood the body, causing physiological and behavioral changes to help moms prepare for their developing baby. However, some alterations, like the ones in the brain, do not go away even after delivery.

Researchers contrasted the behavior of pregnant female mice to that of unpregnant mice. Then, in the hypothalamus, the brain's coordination center, they found a group of particular nerve cells that had previously been connected to parenting behavior.

These nerve cells were shown to contain significant numbers of receptor molecules that bind to the responsive hormones progesterone and estrogen. Removing the pregnant mice from the cells appeared to affect normal parenting behavior but did not affect their virgin counterparts.

They subsequently concentrated on how the binding of these hormones to their receptors affected the brain activity of the mother mice. Estrogen boosted these nerve cells' excitability and decreased their basal activity, but these effects were only temporary. Progesterone did, however, continue to change the animals' brains.

According to Johannes Kohl, group leader of the State-Dependent Neural Processing Laboratory at the Francis Crick Institute and one of the study's co-authors, the two pregnancy hormones - progesterone and estradiol - remodel some neurons in the brain. Shel finds it intriguing that these modifications last a long time and seem to alter the brain permanently. She concluded that pregnancy always affects how these altered neurons are connected to the rest of the brain's parenting network.

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