Is CYP2D6 useful for fertility?

CYP2D6 is a liver enzyme primarily involved in drug metabolism, not directly in fertility. While it does metabolize sex hormones like estrogen and progesterone, and some fertility medications (e.g., clomiphene, tamoxifen), the evidence linking CYP2D6 variants to meaningful fertility outcomes is weak and mostly mechanistic. Small observational studies suggest minor effects on hormone levels, but effect sizes are small and inconsistent. Fertility is a complex trait influenced by age, hormonal balance, lifestyle, and many genetic factors. Therefore, testing CYP2D6 alone is not clinically useful for fertility assessment. Direct-to-consumer DNA tests that claim to predict fertility based on CYP2D6 are overstating the evidence. For genuine fertility concerns, comprehensive clinical evaluation (hormone panels, ovarian reserve testing, semen analysis) is far more informative.