Elena Tsourdi1,2, M Carola Zillikens3. 1. Division of Endocrinology, Diabetes and Metabolic Bone Diseases, Department of Medicine III, Technische Universität Dresden Medical Center, Fetscherstraße 74, 01307, Dresden, Germany. elena.tsourdi@uniklinikum-dresden.de. 2. Center for Healthy Aging, Technische Universität Dresden Medical Center, Dresden, Germany. elena.tsourdi@uniklinikum-dresden.de. 3. Bone Center, Department of Internal Medicine, Erasmus MC, Rotterdam, The Netherlands.