1 Academic Unit of Bone Metabolism, Mellanby Centre for Bone Research, Metabolic Bone Centre, Northern General Hospital, Herries Road, Sheffield, South Yorkshire, S5 7 AU, UK.
2 School of Health and Related Research, University of Sheffield, Sheffield, UK.
3 Academic Unit of Bone Metabolism, Mellanby Centre for Bone Research, Metabolic Bone Centre, Northern General Hospital, Herries Road, Sheffield, South Yorkshire, S5 7 AU, UK. r.eastell@sheffield.ac.uk.