1. Department of Endocrinology & Diabetes, Sir Charles Gairdner Hospital , Nedlands, WA, 6009 , Australia
2. Medical School, University of Western Australia , Crawley, WA, 6009 , Australia
3. Department of Twin Research & Genetic Epidemiology, King's College London , London, SE1 7EH , UK
4. School of Biomedical Sciences, University of Western Australia , Perth, 6009 , Australia
5. Population Health Sciences, University of Leicester , Leicester, LE1 7RH , UK
6. Department of Endocrinology and Metabolism, Odense University Hospital , Odense, 5000 , Denmark