1. Metabolism Unit, Department of Internal Medicine and C.N.R. Institute of Clinical Physiology, University of Pisa School of Medicine, Pisa, Italy
2. Division of Clinical Epidemiology, Department of Medicine, University of Texas Health Science Center at San Antonio, Texas
3. Centro de Estudios en Diabetes, American British Cowdray Hospital and Endocrinology and Metabolism Service, Division of Internal Medicine, Specialty Hospital of the National Medical Center, Mexican Social Security Institute, Mexico City, Mexico