1. Department of Internal Medicine, Chonnam National University Medical School, Gwangju, Korea.
2. Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
3. Department of Internal Medicine, Pusan National University School of Medicine, Busan, Korea.
4. Division of Endocrinology and Metabolism, Department of Medicine, Thyroid Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.