1. Department of Cardiology, University of Groningen and University Medical Center Groningen, 9700 RB Groningen, The Netherlands
2. Labcorp, Morrisville, NC 27560, USA
3. Department of Internal Medicine, Division of Nephrology, University of Groningen and University Medical Center Groningen, 9700 RB Groningen, The Netherlands
4. Department of Internal Medicine, Division of Endocrinology, University of Groningen and University Medical Center Groningen, 9700 RB Groningen, The Netherlands