1. 1Endocrine Section, Department of Internal Medicine, Amsterdam University Medical Center, VUMC, Amsterdam, The Netherlands
2. 2Cork Centre for Vitamin D and Nutrition Research, School of Food and Nutritional Sciences, Department of Medicine, University College Cork, Cork, Ireland
3. 3Calcium Research Unit, Department of Food and Nutritional Sciences, University of Helsinki, Helsinki, Finland
4. 4Department of Geriatrics and Aging Research, University Hospital and University of Zurich, Zurich, Switzerland
5. 5Division of Endocrinology and Diabetology, Department of Internal Medicine, Medical University Graz, Graz, Austria
6. 6Bone Metabolism Unit, Istituto Auxologico Italiano IRCCS, Milano, Italy
7. 7Institute of Rheumatology, Faculty of Medicine, Charles University, Prague, Czech Republic
8. 8Calcium Metabolism and Osteoporosis Program, WHO Collaborating Center for Metabolic Bone Disorders, American University of Beirut Medical Center, Beirut, Lebanon
9. 9Clinic and Laboratory of Endocrinology, Gasthuisberg, KU Leuven, Leuven, Belgium