Biological rhythms and fertility: the hypothalamus–pituitary–ovary axis

Abstract

In addition to normal physiological processes, a number of pathological conditions exhibit diurnal and seasonal fluctuations in their incidence. These biological rhythms are genera ted by the circadian clocks that adjust their functions and adapt to the habitat. Misalignment of biological rhythms and disrupted functions of the circadian clocks may eventually have a negative impact on reproduction, which is the focus of this review. A large body of literature from animal studies has demonstrated the role of core clock genes and clockcontrolled genes in regulation of reproductive events. In contrast, only a few studies, mostly epidemiological ones, suggest that perturbations of the circadian clock functions, eg, due to shift work or jet lag, compromise human reproduction.

Genome-wide association analyses of chronotype in 697,828 individuals provides new insights into circadian rhythms in humans and links to disease

“…Of the traits we tested, we found some evidence that being a morning person may result in a younger age at last childbirth and a reduced risk of multiple pregnancy losses, schizophrenia and depression. Although these results need replication, there is existing evidence of the relationship between circadian rhythms and fertility in women [43][44][45] , and between circadian rhythms and mental health suggesting that this an area for further investigation.…”

Photic Stress and Rhythmic Physiological Processes: Roles of Selenium as a Chronobiotic

“…Suprachiasmatic nucleus of the hypothalamus is known as a master clock as it contains the largest amounts of circadian proteins PERIODS, CRYPTOCHROME, BMAL1, and CLOCK [25]. These proteins are also present in peripheral tissues in the body, where they regulate the timing and oscillation of gene expressions and biological events.…”

“…Yamazaki et al [24] reported that suprachiasmatic nucleus rapidly adjusts to light shifts, but peripheral tissues shift more slowly. For example, PER2 expression in the ovary peaks at light offset delayed by 4-6 hours relative to its expression in the suprachiasmatic nucleus [25]. Also, the duration of light exposure determines whether there will be shifts in the circadian rhythm in both humans and animals [26].…”

“…Works have documented that suprachiasmatic nucleus (SCN) is essential for normal functioning of the hypothalamic pituitary gonadal (HPG) axis [30]. SCN communicates with GnRH neurons through arginine vasopressin (AVP) and vasoactive intestinal peptide (VIP) [25]. The principal afferent pathway to SCN is the photic signal-related retino-hypothalamic pathway.…”