J Clin Endocrinol Metab 2012 Jul 26;97(7):E1327-31. Epub 2012 Apr 26.
Section of Endocrinology and Metabolism, Department of Internal Medicine, Endocrinology and Metabolism, and Biochemistry, University of Siena, Policlinico Santa Maria alle Scotte, Viale Bracci 1, 53100 Siena, Italy.