What role does CLOCK play in fertility?

The CLOCK gene is a core component of the circadian clock, regulating daily rhythms in hormone secretion, metabolism, and reproduction. Disruption of circadian rhythms (e.g., shift work, jet lag) has been associated with menstrual irregularities, reduced fertility, and increased miscarriage risk. CLOCK influences the timing of ovulation, implantation, and even sperm quality. However, the evidence is largely mechanistic and observational; direct genetic testing for CLOCK variants to predict fertility outcomes is not clinically validated. Most studies are small or rely on animal models. Caveat: Fertility is multifactorial; lifestyle, age, and other genetic factors (e.g., ESR1, FSHR) are more established. Consumer DNA tests claiming to assess fertility via CLOCK alone are premature and should be interpreted with caution.