1. Department of Endocrinology (S.S., N.B., J.C.N.), VU University Medical Center, 1007 MB Amsterdam, The Netherlands
2. Department of Rheumatology (N.M.B.), VU University Medical Center, 1007 MB Amsterdam, The Netherlands
3. Division of Bone and Mineral Diseases (X.Z., S.M., M.P.W.), Washington University School of Medicine, St. Louis, Missouri 63110
4. Center for Metabolic Bone Disease and Molecular Research (S.M., M.P.W.), Shriners Hospitals for Children, St. Louis, Missouri 63131