Others have demonstrated that serum 25(OH)D is negatively correlated with serum anti-TPO antibody in HT patients, which was found to be significantly reduced after 4 months of vitamin D supplementation in HT patients [daily oral administration of 1,200–4,000 IU vitamin D3, with the goal of 25(OH)D concentrations of up to 40 ng/mL] (54). This evidence concerns the gene TPO and hematocrit.