1. Department of Internal Medicine I; Endocrine and Diabetes Unit; University Hospital Würzburg; University of Würzburg; Würzburg Germany
2. Medizinische Klinik und Poliklinik IV; Klinikum der Universität München; Munich Germany
3. Department of Endocrinology and Division of Laboratory Research; University Hospital Essen; University of Duisburg-Essen; Essen Germany
4. ENDOC Center for Endocrine Tumors; Hamburg Germany