1. Division of Endocrinology, Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
2. Huh's Diabetes Center and the 21C Diabetes and Vascular Research Institute, Seoul, Korea.
3. Department of Internal Medicine, CHA Bundang Medical Center, CHA University, Seongnam, Korea.
4. Division of Endocrinology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.