1. Division of Endocrinology and Metabolism, Department of Internal Medicine, Helen Joseph Hospital, 1 Perth Road, Rossmore, Johannesburg, South Africa
2. Division of Endocrinology and Metabolism, Department of Internal Medicine, Faculty of Health Sciences, School of Clinical Medicine, University of the Witwatersrand, Johannesburg, South Africa
3. Department of Anatomical Pathology, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa