1. Departments of General Internal Medicine (P.K., A.E.M.), Leiden University Medical Center, 2300 RC Leiden, The Netherlands
2. Departments of Endocrinology and Metabolic Diseases (F.R., H.P.), Leiden University Medical Center, 2300 RC Leiden, The Netherlands
3. Departments of Clinical Chemistry (M.F., J.v.P.), Leiden University Medical Center, 2300 RC Leiden, The Netherlands