Hormones that fluctuate throughout the menstrual cycle might change the brain's structure, a new study suggests.
"Most of what we know about the human body is from studies that were carried out primarily on the male body," said Viktoriya Babenko, a former doctoral student at UCSB, current research specialist at BIOPAC Systems and co-first author of the study, which was posted Oct. 10 to the preprint database bioRxiv and has not yet been peer-reviewed. The other first author was Elizabeth Rizor, a current doctoral candidate in the dynamical neuroscience program at UCSB.
While probing the brain's structure, the study also looked at changes in four hormones throughout the menstrual cycle: estradiol , progesterone, luteinizing hormone and follicle-stimulating hormone . Estrogen and LH levels peak during ovulation, while progesterone peaks during the luteal phase. FSH, in contrast, stays more consistent but also peaks during ovulation, as well as reaching relatively high levels at the end of the luteal phase and during menses.
Although the brain's overall volume stayed the same, increases in progesterone were associated with increases in brain tissue volume but decreases in cerebrospinal fluid, the fluid surrounding the brain that protects it and helps it remove waste. Though the study could have included more people, Rizor and Babenko said the size was typical or even larger than average for an imaging study of this type, especially considering that they collected data from each person at three different times.