The Interplay Between Female Reproductive Function and the Circadian System

Abstract

Female reproductive function and circadian rhythm mutually influence and regulate each other. For example, in adult women, ovarian steroid hormones (oestrogen and progesterone), which affect the circadian rhythm, cause a rapid change in the menstrual cycle, possibly causing sleep disorders. This chapter discusses the relationship between the circadian rhythm and the menstrual cycle (oestrous cycle), which is a part of reproduction. The effect of the oestrous cycle on the circadian rhythm and the effect of the circadian rhythm on female reproductive function” are also reviewed. Our studies using experimental rodent models have demonstrated that disruption of the circadian clock system results in irregular hormonal fluctuations, which are associated with irregular menstruation and ovulation. Exposure to an irregular light environment (lifestyle) disturbs female reproductive function. Collectively, we conclude that it is important to understand sex differences in the biological clock and that leading a regular life considering the biological clock helps maintain a healthy reproductive function. Some of the recent findings reported in the literature concerning the intricate involvement of the circadian system in various physiological processes related to reproduction are further reviewed in the Appendix.