1. Endocrinology Unit I, Department of Clinical and Experimental Medicine, University Hospital of Pisa, Italy.
2. Unit of Internal Medicine and Endocrinology, Fondazione Salvatore Maugeri, University of Pavia, Pavia, Italy.
3. Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Phoenix, Arizona.