Radioactive iodine in the management of thyrotoxicosis.

Abstract

Objective : An audit of the use and outcomes of Radioactive Iodine (RAI) therapy in the definitive management of thyrotoxicosis at Inkosi Albert Luthuli Central Hospital (IALCH), KwaZulu-Natal, South Africa. Methods : The clinical records of all new patients with thyrotoxicosis, referred in a 4 year period between 01/01/2003 and 31/12/2006, were analysed. Response to RAI was monitored using biochemical parameters (namely, Thyroid Stimulating Hormone and Free T4 levels). Rates of euthyroidism (cure), hypothyroidism and hyperthyroidism (treatment failure) were correlated to dose of RAI. Patients were followed-up for at least 2 years or until the onset of hypothyroidism. The follow-up period was until 31/12/2007. Results : One hundred and fourteen patients (37.7%), of a cohort of 302 new thyrotoxic patients treated with RAI, met the inclusion criteria. Ninety-six patients (84.2%) had Graves Disease (GD) whilst 18 had Toxic Nodular Disease (TND). At 2 year follow-up, 91 patients (79.8%) were hypothyroid, 10 (8.8%) were euthyroid and 13 (11.4%) were hyperthyroid. The average dose of RAI to achieve euthyroidism was 10mCi and hypothyroidism, 9.7mCi. The average time to achieve euthyroidism was 5.9 months and 10.1 months to become hypothyroid. Thirty-one patients (27.2%) remained persistently hyperthyroid after one dose of RAI. Patients with GD (88.5%) were more likely to become hypothyroid (p < 0.001) whilst 38.9% of TND patients remained hyperthyroid (p = .001). Baseline TFT values were significant in terms of outcomes correlated with the prescribed RAI dose i.e Low Dose (<8mCi) vs. Intermediate Dose (8-9mCi) vs. High Dose (>9mCi)(TSH p = 0.05; FT4 p = 0.003; FT3 p = 0.001). Conclusion : The majority of patients became hypothyroid over time, in keeping with reported data. In the public health sector, where early access to RAI (in terms of waiting times for appointments for RAI) and follow-up are major problems, early cure is essential to minimize the morbidity of thyrotoxicosis and this may be achieved with an initial high dose of RAI.