1. Duke Clinical Research Institute, Durham, North Carolina
2. Department of Biostatistics, Duke University, Durham, North Carolina
3. Department of Medicine, Duke University, Durham, North Carolina
4. Section of Endocrine Surgery, Department of Surgery, Duke University Medical Center, Durham, North Carolina
5. Duke Clinical Research Institute, Durham, North Carolina4Section of Endocrine Surgery, Department of Surgery, Duke University Medical Center, Durham, North Carolina