New Study Investigates the Menstrual Cycle's Effect on the Brain
Researchers have shown that fluctuations in ovarian hormones during the menstrual cycle can affect plasticity in key brain regions.
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Central learning and memory hubs change in response to sex hormones. A new study in Nature Mental Health by Rachel Zsido and Julia Sacher of the Max Planck Institute for Human Cognitive and Brain Sciences and the University Clinic in Leipzig, Germany, links rhythmic oscillations in ovarian hormone levels in women during the menstrual cycle to changes in brain structure.
Ovarian hormones have significant effects on the brain, and early menopause may be associated with an increased risk of accelerated brain aging and dementia later in life. However, the effects of ovarian hormone fluctuations on brain structure earlier in life are less defined. In their current study, Rachel Zsido and Julia Sacher show that fluctuations in ovarian hormones affect structural plasticity in key brain regions during the reproductive years.
To do this, the scientists collected blood samples from 27 female study participants, used ultrasound to track follicle growth in the ovaries to pinpoint ovulation timing, and utilized ultra-high field 7 Tesla MRI to zoom into subregions of the medial temporal lobe and hippocampus. That's because these regions are dense with sex hormone receptors and are critical for cognitive function, such as episodic memory.
Capturing dynamic changes in sex hormones
Unlike previous studies, Zsido and Sacher examined female brains not just at one point in time, but at six points across the menstrual cycle. This longitudinal design captures the dynamic changes in sex hormones - during the menstrual cycle, estradiol increases across the first half of the cycle and peaks around ovulation, while progesterone dominates the second half of the cycle. Estradiol is one of the most important sex hormones in the female body and is instrumental in maintaining the reproductive system. Progesterone is another key sex hormone for the reproductive system that prepares the uterus for pregnancy and has anxiety-relieving, sleep-inducing, relaxing and calming effects. So, much like the ebb and flow of the tide, the female brain is attuned to a constant rhythm of hormones, which this research study maps for the first time.
Reference: Zsido RG, Williams AN, Barth C, et al. Ultra-high-field 7T MRI reveals changes in human medial temporal lobe volume in female adults during menstrual cycle. Nat Mental Health. 2023;1(10):761-771. doi: 10.1038/s44220-023-00125-w
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