Department of Rheumatology, Endocrinology and Nephrology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan. Clinical Research and Medical Innovation Center, Hokkaido University Hospital, Sapporo, Japan. Division of Diabetes and Endocrinology, Department of Medicine, NTT Sapporo Medical Center, Sapporo, Japan. Third Department of Internal Medicine, Hokkaido P.W.F.A.C Obihiro-Kosei General Hospital, Obihiro, Japan. Department of Diabetes Centre, Manda Memorial Hospital, Sapporo, Japan. Department of Internal Medicine, Jiyugaoka Medical Clinic, Obihiro, Japan. Sapporo Diabetes and Thyroid Clinic, Sapporo, Japan. Aoki Clinic, Sapporo, Japan. Kurihara Clinic, Sapporo, Japan. Division of Diabetes and Obesity, Faculty of Medicine and Graduate School of Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan.