Lorenz C Hofbauer1, Tilman D Rachner2. 1. Division of Endocrinology, Diabetes, and Bone Diseases, Technische Universität Dresden Medical Center, 01307 Dresden, Germany; Center for Regenerative Therapies Dresden, Germany. Electronic address: lorenz.hofbauer@uniklinikum-dresden.de. 2. Division of Endocrinology, Diabetes, and Bone Diseases, Technische Universität Dresden Medical Center, 01307 Dresden, Germany.