1. Division of Geriatric Medicine, Department of Internal Medicine, Helen Joseph Hospital, Johannesburg, South Africa
2. Division of Geriatric Medicine, Department of Internal Medicine, School of Clinical Medicine, University of the Witwatersrand, Johannesburg, South Africa
3. Division of Endocrinology and Metabolism, Department of Internal Medicine, Helen Joseph Hospital, Johannesburg, South Africa
4. Division of Endocrinology and Metabolism, Department of Internal Medicine, School of Clinical Medicine, University of the Witwatersrand, Johannesburg, South Africa
5. Department of Chemical Pathology, National Health Laboratory Services, Helen Joseph Hospital, Johannesburg, South Africa
6. Department of Chemical Pathology, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa