How are CLOCK and Fruchtbarkeit related?

The relationship between the CLOCK gene and fertility is not yet firmly established in human research. CLOCK (Circadian Locomotor Output Cycles Kaput) is a core circadian gene that regulates the body's internal clock. Disruption of circadian rhythms—due to shift work, jet lag, or sleep disorders—has been associated with reduced fertility, including menstrual irregularities, altered hormone secretion (e.g., melatonin, LH, FSH), and poorer oocyte quality. Mechanistic and animal studies suggest that CLOCK variants may influence ovarian function and implantation success. However, large-scale human studies directly linking specific CLOCK polymorphisms to fertility outcomes are lacking. Most evidence is mechanistic or from GWAS with small effect sizes. Consumer DNA tests that claim to predict fertility based on CLOCK variants are not supported by robust clinical evidence. The evidence level is mechanistic. Caveat: lifestyle factors (sleep, stress, nutrition) have a much stronger impact on fertility than common CLOCK variants.