In the field of human neuroscience, most research has focused on elucidating the impact of menstrual cycle-driven hormonal changes on the patterns of brain communication during cognitive or affective tasks. However, there remains a significant gap in understanding how these hormones specifically affect the anatomical pathways and nodes that facilitate such communication. A recent study conducted in Santa Barbara has made a groundbreaking discovery, demonstrating that female sex hormones have effects on brain structure beyond the traditional understanding of the hypothalamic-pituitary-gonadal axis. Essentially, these hormones play a role beyond reproductive functions. The study, conducted by a commendable team of female neuroscientists, marks a significant stride in understanding complex aspects of menstrual health.

The research revealed the following things:

1. An increase in oestrogen and LH just before ovulation impacts white matter in the brain, potentially leading to faster processing times. 
2. Additionally, FSH, initiating the follicular phase, affects grey matter thickness, particularly in the temporal and occipital lobes, suggesting an influence on limbic and visual systems. 
3. Progesterone, associated with increased tissue and decreased cerebrospinal fluid volumes, could have significant implications for behaviour, cognition, and clinical outcomes in diverse areas, including menstrual health, Alzheimer's risk, and brain injuries in females. 

Who is this study about and why?

This study focused on women aged 18-29 across three menstrual cycle phases: menstruation, ovulation, and mid-luteal phase. The aim was to investigate whether fluctuations in brain levels (LH and FSH) and sex hormones (oestrogen and progesterone) influence brain structure. Specifically, the study examined white matter, cortical thickness, brain volumes, and grey matter. These hormones exert effects beyond the uterus, influencing the brain's plasticity and neural communication. Understanding the impact of these hormonal changes on the brain can provide insights into the behavioural, emotional, and cognitive effects of the menstrual cycle. This knowledge is crucial for dispelling stereotypes and could have implications for conditions like Alzheimer's disease and female-specific brain injuries.

How does it impact everyday lives of women?

For individuals experiencing monthly menstrual cycles, the study discovered that FSH influences the thickness of grey matter in the temporal and occipital lobes, indicating an impact on the limbic system associated with emotions and behavioural responses. Since FSH is elevated just before ovulation in the follicular phase, these effects are likely more pronounced in the first half of the menstrual cycle. Furthermore, Oestrogen, LH, and FSH were linked to an increase in white matter, suggesting enhanced communication within the brain. This effect was prominent during the ovulation phase or just before ovulation, which could potentially influence psychological processes and cognition in women during this menstrual cycle phase.

In the case of progesterone, the hormone was found to both increase and decrease the brain's cerebrospinal fluid level, a complex aspect that requires further explanation from neuroscientists. An intriguing finding was that women who experienced painful periods in their life showed an increase in grey matter in the pain centres of the brain during their menstrual cycle. This suggests that heightened thickness in these areas could amplify pain signals, providing insights into the experience of pain during menstruation.

What does this mean for future research?

Although the present study boasts a more extensive sample size compared to numerous prior research endeavours on the menstrual cycle, the establishment of brain-hormone associations at the population level necessitates more extensive consortium studies. The study's participants were exclusively adults under 30 at the time, but given that menstrual cycle-driven brain-hormone associations might undergo changes across the lifespan, additional investigations involving younger and older age groups are imperative to comprehensively grasp this intricate relationship. Larger collaborative efforts would contribute to a more thorough understanding of how hormonal influences on the brain evolve over time and their implications across various age demographics.

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References

Instagram | Bump Fitness | BioRxiv | Max-Planck- Gesellschaft | National Library of Medicine | The Women’s Center | Neuropsychopharmacology