1. Division of Endocrinology and Metabolism, Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
2. Division of Health and Nutrition Survey, Korea Centers for Disease Control and Prevention, Cheongju, Korea.
3. Division of Endocrinology and Metabolism, Department of Medicine, Thyroid Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
4. Department of Social and Preventive Medicine, Sungkyunkwan University School of Medicine, Suwon, Korea.
5. Department of Surgery, Chungbuk National University College of Medicine, Cheongju, Korea.
6. Department of Surgery, CHA Gangnam Medical Center, CHA University, Seoul, Korea.