These were located in or near <i>GC</i>, the vitamin D binding protein, or <i>CYP2R1</i>, a cytochrome P450 enzyme that hydroxylates vitamin D to form 25(OH)D. The top hit was rs4588, a missense <i>GC</i> polymorphism associated with a 3.5 ng/mL decrease in 25(OH)D per copy of the minor allele (95% confidence interval [CI]: -4.1, -3.0; <i>p</i> = 4.5 × 10<sup>-38</sup>).