1 National Research Council (CNR)-Institute of Clinical Physiology (IFC), Pisa, Italy; Department of Medicine, University of Padova Italy; Padova, Italy. Electronic address: dante.lucia@libero.it.
2 Servicio de Metabolismo Óseo y Mineral, Instituto Reina Sofía de Investigación, REDinREN del ISCIII, Hospital Universitario Central de Asturias, Universidad de Oviedo, Oviedo (Asturias), España.
3 Department of Medicine, Division of Nephrology, Columbia University Medical Center, New York, New York, USA.
4 Laboratory Medicine Unit, Department of Medicine, University of Padova, Padova, Italy.
5 Ospedale N.S. di Bonaria, S. Gavino Monreale, Italy.
6 Department of Medicine, Clinica Medica 1, University of Padova, Padova, Italy.
7 Nephrology and Dialysis Unit, Ospedale San Carlo Borromeo, Department of Clinical and Biomedical Sciences "Luigi Sacco," University of Milan, Milan, Italy.