1. Department of Internal Medicine I, Division of Endocrinology, Diabetes and Metabolism, University Hospital Frankfurt, Frankfurt am Main, Germany.
2. Endocrinology, Hospital Clinic, Institut d’Investigacions Biomediques August Pi i Sunyer, Barcelona, Spain.
3. Red Cross Blood Transfusion Center, Institute of Transfusion Medicine and Immunohaematology, Frankfurt am Main, Germany.