Evidence that the woman's ovarian cycle is driven by an internal circamonthly timing system

Area of Science:

• Chronobiology
• Reproductive Endocrinology
• Epidemiology

Background:

• The circa-monthly rhythm of the ovarian cycle is well-established.
• The underlying mechanisms driving the regularity of the ovarian cycle remain largely unknown.
• Potential drivers include endogenous clocks or external/internal processes.

Purpose of the Study:

• To investigate the driving mechanisms behind the regularity of the ovarian cycle.
• To determine if an endogenous clock or other factors are responsible for the menstrual cycle's rhythm.
• To explore potential influences of the lunar cycle on ovarian cyclicity.

Main Methods:

• Analysis of two large epidemiological datasets comprising 26,912 cycles from European women and 4786 cycles from North American women.
• Application of time series and circular statistical analyses to evaluate cycle regularity.
• Comparison of endogenous clock mechanisms against other internal and external process models.

Main Results:

• Evidence suggests an endogenous clock-like mechanism is the most probable driver of the ovarian cycle's rhythm.
• A weak but significant influence of the 29.5-day lunar cycle on the menstrual cycle was observed.
• Phase alignment between the ovarian and lunar cycles varied between European and North American populations.

Conclusions:

• The findings support an endogenous clock as the primary regulator of ovarian cycle rhythmicity.
• The lunar cycle shows a subtle but statistically significant association with the menstrual cycle.
• Further research in larger populations and evaluation of chronobiological approaches are recommended for subfertility treatments.