The significant negative correlations between 25(OH)D and 1–84 PTH, as well as 1,25(OH)2D and 1–84 PTH levels, suggest that adequate cholecalciferol supplementation with adequate 25(OH)D and 1,25(OH)2D levels may play an important role in mitigating parathyroid gland overactivity in the HD patients population. This evidence concerns the gene PTH and Huntington disease.