The hormonal fluctuations that regulate the menstrual cycle not only affect the reproductive anatomy but also impacts brain dynamics. A new study provides insight into how this happens.
A team of researchers at the University of California, Santa Barbara, led by neuroscientists Elizabeth Rizor and Viktoriya Babenko, tracked the menstrual cycles of 30 women and thoroughly documented the structural changes that take place in the brain with variations in hormone levels.
The results suggest structural changes in the brain during menstruation, which may not just be confined to the regions associated with the menstrual cycle. However, the results are yet to be peer-reviewed and can be found on the preprint server ‘bioRxiv’.
The results demonstrated that the hormonal fluctuations led to changes in gray and white matter volumes as well as the volume of cerebrospinal fluid.
In particular, when the levels of the hormones 17-beta-estradiol and luteinizing hormone rose just before ovulation, the brains of the participants showed white matter changes, suggesting faster information transfer.
Follicle-stimulating hormone, which ascends before ovulation and helps stimulate the ovary follicles, was associated with thicker gray matter.
Progesterone, a hormone that surges after ovulation, was associated with increased tissue and decreased cerebrospinal fluid volume, with total brain volume remaining unchanged.
The researchers wrote that these results are the first to report simultaneous brain-wide changes in human white matter microstructure and cortical thickness coinciding with menstrual cycle-driven hormone rhythms. The authors propose that the effects resulting from brain-hormone interactions may not necessarily be restricted to classically known hypothalamic-pituitary-gonadal-axis (HPG-axis) receptor-dense regions.
The hormonal shifts that occur during puberty, oral contraception use, gender-affirming hormone therapy, and postmenopausal estrogen therapy have been found to alter the microstructure of white matter - the fatty network of neuronal fibers that allows the exchange of information between regions of gray matter.
Most of the research conducted to examine the hormonal effect on the brain has concentrated on brain communication during cognitive tasks rather than the actual structures themselves.
Cyclic fluctuations in HPG-axis hormones influence the mammalian central nervous system, exerting powerful behavioral, structural, and functional effects. However, there is limited understanding of how these fluctuations alter the structural nodes and information highways in the human brain.
We do not currently report functional consequences or correlates of structural brain changes, our findings may have implications for hormone-driven alterations in behavior and cognition,“ wrote the researchers.
The authors conclude that ‘investigation of brain-hormone relationships across networks is necessary to understand human nervous system functioning on a daily basis, during hormone transition periods, and across the human lifespan.’
Women are likely to experience around 450 menstrual cycles in the course of their lifetime. The research could be instrumental in launching future studies, potentially offering insights into the causes of unusual but severe mental health problems related to the menstrual cycle.
1) Rizor, Elizabeth J., Viktoriya Babenko, Neil M. Dundon, Renee Beverly-Aylwin, Alexandra Stump, Margot Hayes, Luna Herschenfeld-Catalan, Emily G. Jacobs, and Scott T. Grafton. "Menstrual cycle-driven hormone concentrations co-fluctuate with white and grey matter architecture changes across the whole brain." bioRxiv (2023): 2023-10.
(Input from various media sources)
(Rehash/Dr. Vineesha V/MSM)
