A mendelian randomization study based on three single nucleotide variants associated with 25(OH)D levels: rs2282679, rs10741657, and rs12785878, related to the genes GC, CYP2R1 and DHCR7, respectively, found that a 10% increase in serum 25(OH)D levels causes a 0.3% decrease in eGFR (53), while there was no effect of VitD supplementation of 4,000 IU per day versus placebo for a median duration of 2.9 years on changes in eGFR in adults with prediabetes (54), though there were no data of serum creatinine available in the above two studies. This evidence concerns the gene CYP2R1 and prediabetes syndrome.