Myths vs facts: VDR and fertility

The vitamin D receptor (VDR) is frequently linked to fertility, but many claims are overstated. Fact: VDR is a nuclear receptor regulating gene expression, calcium homeostasis, and immune function. Observational studies have associated certain VDR polymorphisms (e.g., FokI, TaqI) with female fertility outcomes such as endometriosis or PCOS. However, effect sizes are small, results are inconsistent, and no causal relationship has been established. Importantly, circulating vitamin D levels (25(OH)D) appear to have a stronger impact on reproductive health than VDR genotype. The evidence is predominantly from mechanistic and association studies; robust randomized trials are lacking. Therefore, marketing VDR genetic tests as fertility predictors is misleading. Clinical relevance remains uncertain, and supplementation should be guided by measured vitamin D status, not genotype. Conclusion: VDR variants are a minor piece of the puzzle, not a fertility indicator. Evidence is mixed and insufficient for clinical recommendations.