1. Department of Internal Medicine, Seoul National University College of Medicine , Seoul 03080 , South Korea
2. Department of Internal medicine, Seoul National University Hospital , Seoul 03080 , South Korea
3. Department of Internal Medicine, Seoul National University Bundang Hospital , Sungnam 13620 , South Korea
4. Division of Endocrinology and Metabolism, Department of Internal Medicine, Boramae Medical Center , Seoul 07061 , South Korea
5. Division of Endocrinology, Department of Internal Medicine, Healthcare System Gangnam Center, Healthcare Research Institute, Seoul National University Hospital , Seoul 06236 , South Korea