An analysis of the factors influencing outcome of radioiodine therapy in African patients' with graves' disease

Bhana, Motala Purbhoo
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Background Graves’ disease is one of the commonest causes of hyperthyroidism worldwide and amongst our African population. Radioiodine ablation is a treatment modality used to treat Graves’ disease. Despite its success in treating the disease, there are a number of patients that will require a second or third ablation to adequately control the hyperthyroid state. It is thus important to document this percentage in our setting, and the role that any pre-treatment factors play in determining outcome following radioiodine ablation. Objectives To determine the percentage of patients that require a single, second, and third dose of radioiodine. In addition, to identify factors that may predict a poor response to radioiodine ablation. Methods Two hundred adult patients that underwent radioiodine ablation for Graves’ disease at Chris Hani Baragwanath Hospital until 30 June 2015 were included in the study. Information was obtained from the medical records from the Departments of Endocrinology, and Nuclear Medicine and captured onto a data sheet. Results The total sample of 191 African patients were predominantly female (83%) and between the ages of 40 – 60 years old (52%). Ninety-eight percent of the patients had a TSH value that was suppressed at admission. Seventy-eight percent of the patients had a single radioiodine ablation; twenty percent of the patients had two ablations, and two percent of the patients had had three ablations. At twelve months post ablation, seventy-two percent of the patients had a TSH value that was normal or high, with only twenty-two percent having a TSH value that was still suppressed. There was no statistically significant relationship between age, gender, and TSH level with treatment outcome. The level of FT4 at three months was significantly associated with treatment outcome at three months post ablation with a higher FT4 level associated with treatment failure and subclinical hyperthyroidism. This was not seen at six or twelve months. Treatment with anti-thyroid drugs prior to ablation was not significantly associated with treatment outcome. Conclusion This study concluded that seventy-eight percent of patients required a single ablation with twenty percent requiring a second ablation and two percent requiring a third ablation. The FT4 level at three months was significantly associated with treatment outcome, but this was not seen at six or twelve months post ablation. There was no statistically significant association between age, gender, TSH level, FT4 level at six and twelve months, thyroid antibodies, Graves’ eye disease, thyroid morphology, and the use of anti-thyroid drugs with treatment outcome.
A research article submitted to the Faculty of Health Sciences, University of the Witwatersrand, in partial fulfilment for the degree of MMED: Internal Medicine Johannesburg, September 2019