1. Department of General, Visceral, and Transplant Surgery, Ludwig-Maximilians-University Munich, 81377 Munich, Germany
2. Department of Internal Medicine I, Division of Endocrinology and Diabetes, University Hospital, University of Wuerzburg, 97080 Wuerzburg, Germany
3. Central Laboratory, Core Unit Clinical Mass Spectrometry, University Hospital, University of Wuerzburg, 97080 Wuerzburg, Germany
4. Department of General and Visceral Surgery, Sana-Krankenhaus Huerth GmbH, 50354 Huerth, Germany