Objective: The aim of our audit was to determine the effectiveness of first dose Radioiodine (RAI) in curing thyrotoxicosis, comparing our results with published rates of success and hypothyroidism.
Methods: All patients with thyrotoxicosis treated with RAI between 2002 2004 (n=71) were identified and casenotes reviewed. Patients were either given nominal doses of either 259 or 407 MBq. Data collected included: the cause of thyrotoxicosis, goitre size, starting free T4 levels, dose of antithyroid medication prior to radioiodine, dose of radioiodine given and thyroid function 6 months and 1 year following RAI.
Results: Fifty three (75%) subjects were female and the median age of diagnosis was 59 years. A moderate or large goitre was found in 18 (25%) patients. The mean starting FT4 level was slightly higher in patients with Graves disease compared with Toxic nodular disease (46 vs 40 mmol/L, P=0.01). Patients with Graves disease were given a lower dose of RAI compared with those with Toxic nodular disease (333 vs 382 MBq, P<0.01). 62% of patients with Graves disease were either euthyroid or hypothyroid 6 months following treatment compared with 79% of patients with a toxic nodule or multinodular goitre (P=0.009). Only the dose of RAI and the presence of a goitre were related to treatment failure. 50% of patients receiving 259 MBq were still thyrotoxic at 6 months compared with 18% of patients who had received 407 MBq (P<0.005). 28% of patients with Graves disease and 21% of those with toxic nodular disease became hypothyroid 1 year following RAI (P=NS).
Conclusions: This audit identifies a relatively high failure rate in patients given a dose of 259 MBq although our rates of early hypothyroidism are low compared with the published literature. The results of this audit will be used to inform patients about the pros and cons of both treatment doses.