1. Department of Visceral, Vascular and Endocrine Surgery, Faculty of Medicine, Martin Luther University Halle-Wittenberg , D-06097 Halle (Saale) , Germany
2. Department of Endocrinology, Diabetology and Metabolism, University of Duisburg-Essen , D-45122 Essen , Germany
3. Department of General, Visceral and Transplantation Surgery, Division of Endocrine Surgery, University of Duisburg-Essen , D-45122 Essen , Germany