The goal of this clinical trial is to determine individual-level genetic and metabolic
characteristics that modify the response to cholecalciferol treatment.
This study is double blind, parallel design, randomized clinical trial that will assess
genetic and metabolic characteristics that modify the response to cholecalciferol treatment.
. Eligible participants will be randomly assigned to receive cholecalciferol treatment (2,000
international units of cholecalciferol daily by mouth) or placebo in a 3:1 ratio for a total
duration of 16-weeks. The planned sample size is 1,600. The primary aim of this study is to
identify genetic polymorphisms, clinical characteristics, and biomarkers that modify the
biologic response to vitamin D3 treatment, assessed by changes in serum concentrations of
parathyroid hormone (PTH) and 1,25(OH)2D and urine calcium excretion.