Imaging Study Details the Menstrual Cycle’s Effects on the Brain

The body undergoes several physiological during the menstrual cycle, driven by hormonal fluctuations. But how do these hormones impact the brain?

A new study, published in Nature Mental Health, investigated how rhythmic oscillations in hormones shape brain structure during the reproductive years.

Understanding the rhythmic flow of sex hormones

Estradiol is a crucial sex hormone in the female body, which dominates during the first half of the menstrual cycle and peaks during ovulation. Similarly, progesterone plays a vital role, peaking five to nine days after the luteal phase in the second half of the cycle.

Ovarian hormones have been found to impact the brain previously. Studies have shown that early menopause may be associated with an increased risk of brain aging and dementia. However, there is a lack of research concerning how these hormones may impact brain structure earlier in life.

Ovarian hormone fluctuations shape structural brain plasticity

 Dr. Julia Sacher, professor in the department of neurology at the Max Planck Institute, and colleagues collected blood samples from 27 female participants to measure their hormone levels to determine where they were in their cycle.

Ultra-high field 7 Tesla MRI was used to capture the subregions of the medial temporal lobe and hippocampus, areas of the brain that are dense with sex hormone receptors, at six time points during the menstrual cycle:

• Menstrual (<five days menses onset)
• Pre-ovulatory (≤two days before ovulation)
• Ovulation (≤24 h of ovulation)
• Post-ovulatory (≤two days after ovulation)
• Mid-luteal (six to 8 days after ovulation) and
• Premenstrual (≤three days next menses onset).

Sacher and team found particular regions in the medial temporal lobe, vital for episodic memory and spatial cognition, expanded when estradiol levels increased, and progesterone levels decreased.

These changes in brain structure were concealed when analzying the hippocampus as a whole, demonstrating a potential limitation of studies that traditionally assess the hippocampus as a single structure.

"We were able to determine that these brain areas remodel themselves in synchronization with the menstrual cycle,” said Sacher.

Exploring hormonal influences on memory and mood disorders

The team plans to investigate whether these rhythmic changes may be altered in individuals at risk for memory and affective disorders.

"In general, the female brain is still massively understudied in cognitive neuroscience. Even though sex steroid hormones are powerful modulators of learning and memory, less than 0.5% of the neuroimaging literature considers hormonal transition phases, such as the menstrual cycle, the influence of hormonal contraceptives, pregnancy and menopause,” Sacher said.

“We are committed to addressing this fundamental research gap. To identify the mechanisms underlying risk and resilience to mental health disorders, such as depression or Alzheimer’s disease, we need a deeper understanding of how the healthy female brain adapts to change," Sacher concluded.

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

This article is a rework of a press release issued by the Max Planck Institute. Material has been edited for length and content.