1. VA North Texas Health Care Services , Dallas TX , USA
2. Department of Medicine and Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, UT Southwestern Medical Center , Dallas, TX , USA
3. Department of Medicine, University of Louisville Health Sciences Center , Louisville, KY , USA
4. Nephrology and Internal Medicine, Mansoura University , Mansoura , Egypt
5. Robley Rex VA Medical Center , Louisville, KY , USA