California, US Edited By: Sneha Swaminathan Updated: Oct 22, 2023, 02:29 PM IST
The intricate hormonal fluctuations that regulate the menstrual cycle don’t just affect the reproductive organs; they also shape the brain. A recent study led by neuroscientists Elizabeth Rizor and Viktoriya Babenko from the University of California Santa Barbara offers new insights into this process.
The study, though awaiting peer review, is available on the preprint server bioRxiv and meticulously tracks structural brain changes during hormonal fluctuations throughout the menstrual cycle.
The findings indicate that structural changes in the brain during menstruation go beyond regions typically associated with the menstrual cycle. According to the researchers, these results are the first to report concurrent changes in white matter microstructure and cortical thickness throughout the entire brain, coinciding with the hormonal variations of the menstrual cycle.
This suggests that the influence of hormones on the brain may extend to regions not traditionally associated with menstrual hormones.
With women who menstruate experiencing approximately 450 menstrual cycles in their lifetime, understanding the diverse effects of these hormonal changes on the body is crucial.
Surprisingly, research on this topic has been somewhat limited, considering that half of the world’s population goes through this process for half of their lives.
A gap in understanding
Research on the hormonal impact on the brain has primarily focused on brain communication during cognitive tasks rather than examining the structural changes in the brain itself. Hormonal fluctuations have been found to affect the microstructure of white matter, which plays a crucial role in transmitting information between grey matter regions. These shifts have been observed during various life stages, including puberty, oral contraceptive use, gender-affirming hormone therapy, and post-menopausal estrogen therapy.
To address this gap in knowledge, the research team conducted MRI scans of participants during three menstrual phases: menstruation, ovulation, and mid-luteal. Simultaneously, they measured the participants’ hormone levels.
The results revealed that as hormone levels fluctuate, both grey and white matter volumes in the brain, as well as the volume of cerebrospinal fluid, undergo changes. Notably, just before ovulation, when 17β-estradiol and luteinising hormone levels rise, white matter changes suggestive of faster information transfer were observed. Follicle-stimulating hormone, which surges before ovulation and assists in stimulating ovary follicles, was associated with thicker gray matter. In contrast, post-ovulation, when progesterone levels rise, the research linked this to increased tissue and decreased cerebrospinal fluid volume.
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