Based on our findings, which indicated no correlation between serum 1,25(OH)2D3 concentrations and CYP24A1 and CYP27B1 mRNA levels in PBMCs of T1DM patients, we further investigated whether epigenetic factors such as miRNAs might play a role in regulating CYP27B1 expression. The gene discussed is CYP24A1; the disease is type 1 diabetes mellitus.