Doxercalciferol (Hectorol) is a synthetic analog of vitamin D. Doxercalciferol (Hectorol) is used for the treatment of secondary hyperparathyroidism. Doxercalciferol (Hectorol) acts to replace the deficient production of vitamin D metabolites. Doxercalciferol (Hectorol) is converted to an active vitamin D metabolite by the body and acts by reducing the production of excess PTH by the parathyroid gland. This reduces the development of metabolic bone disease