Department of Metabolism and Endocrinology, The Second Xiangya Hospital, Central South University, Changsha, China. Key Laboratory of Diabetes Immunology (Central South University), Ministry of Education, National Clinical Research Center for Metabolic Diseases, Changsha, China. Division of Endocrinology, Metabolism, and Nutrition, Rutgers University-Robert Wood Johnson Medical School, New Brunswick, New Jersey. Department of Endocrinology, Heji Hospital Affiliated to Changzhi Medical College, Changzhi, China. Department of Endocrinology, The First Affiliated Hospital and College of Clinical Medicine of Henan University of Science and Technology, Luoyang, China. Department of Epidemiology and Health Statistics, Xiangya School of Public Health, Central South University, Changsha, China.