Myths vs facts: CLOCK and fertility

The claim that the CLOCK gene directly determines fertility is a myth. CLOCK (Circadian Locomotor Output Cycles Kaput) is a core circadian gene. Mechanistic evidence suggests that disrupted circadian rhythms—e.g., from shift work or poor sleep—can alter hormone secretion (melatonin, cortisol, LH, FSH) and thereby affect fertility. However, the evidence for individual CLOCK variants as a standalone cause of fertility problems is weak. Most studies are animal-based or observational, lacking causal proof. A DNA test for CLOCK polymorphisms, such as those offered by MyBody-X or other companies, cannot reliably predict personal fertility. Effect sizes are small, and environmental factors (stress, diet, sleep) play a much larger role. Fact: A healthy lifestyle with a consistent sleep-wake cycle supports fertility, but a CLOCK gene test is unnecessary for that. For unresolved infertility, medical evaluation is essential, not a home DNA test.