[1] Boston Univ, Med Ctr, Dept Med, Vitamin D Skin & Bone Res Lab, Boston, MA 02118 USA
[2] Free Univ Berlin, Klinikum Benjamin Franklin, Inst Med Stat, Dept Nat Med, Berlin, Germany
[3] Free Univ Berlin, Klinikum Benjamin Franklin, Dept Internal Med, Div Endocrinol & Nephrol, Berlin, Germany