Menstrual Cycle Hormone Fluctuations Can Alter Brain Network Dynamics
Hormonal fluctuations during the menstrual cycle influence brain network dynamics.
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A recent study from Pompeu Fabra University reveals that hormonal fluctuations during the menstrual cycle lead to changes in brain network dynamics. Published in npj Women's Health, the research aims to contribute to a deeper understanding of menstrual cycle-related disorders.
Menstrual cycle hormones impact physiological processes
The menstrual cycle is a natural process that is primarily regulated by the hormones estrogen and progesterone. These hormones fluctuate throughout the menstrual cycle, typically spanning 28 days, and are essential for reproductive health.
Menstrual cycle phases
- Menstruation (Days 1–5): The uterine lining sheds, triggered by a decrease in estrogen and progesterone levels.
- Follicular phase (Days 6–14): The pituitary gland releases follicle-stimulating hormone (FSH), prompting the maturation of ovarian follicles. These follicles, in turn, produce estrogen, initiating the thickening of the uterine lining in preparation for potential pregnancy.
- Ovulation (Day 14): There is a surge in luteinizing hormone (LH) that triggers the release of a mature egg from the ovary.
- Luteal phase (Days 15–28): The ruptured follicle transforms into the corpus luteum, secreting progesterone to maintain the uterine lining in anticipation of implantation.
Beyond their roles in fertility, these hormonal changes also influence a variety of physiological processes, including brain function. Recent neuroimaging studies have shown changes in brain activity across the cycle, but many of these had a small sample size or lacked whole-brain dynamic analyses. Research centered on how hormonal shifts influence overall brain activity is still limited, with most studies focusing on specific regions rather than examining the global functioning of brain networks.
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The researchers investigated how brain network dynamics change during the menstrual cycle using functional magnetic resonance imaging (fMRI). Resting state scans were taken of 60 naturally cycling women, aged 18–35 years old, across three menstrual phases: early follicular, pre-ovulatory and mid-luteal. They specifically analyzed how different brain networks involved in attention, emotions and introspection evolved during the resting state.
"We show that ovarian hormones modulate the dynamics of the entire brain throughout the menstrual cycle," said corresponding author Dr. Anira Escrichs, a computer engineer at Pompeu Fabra University.
Escrich and their team found that levels of brain complexity depended on the levels of estrogen and progesterone. The highest amount of dynamical complexity was found in the pre-ovulatory phase, when estrogen is at its highest, and the lowest was displayed during the early follicular phase when progesterone begins to rise.
Further research
Understanding how hormones influence brain dynamics across the menstrual cycle will provide further insight into the cognition, mood and behavior of healthy women as well as those impacted by menstrual cycle-related disorders.
The researchers comment that further investigations are needed to replicate their study due to inconsistent results in the field.
Reference: Avila-Varela DS, Hidalgo-Lopez E, Dagnino PC, et al. Whole-brain dynamics across the menstrual cycle: the role of hormonal fluctuations and age in healthy women. npj Women’s Health. 2024;2(1):8. doi: 10.1038/s44294-024-00012-4
This article is a rework of a press release issued by Pompeu Fabra University. Material has been edited for length and content.
