Outcomes after radioiodine treatment for thyrotoxicosis

BackgroundRadioiodine is commonly prescribed as a permanent treatment for thyrotoxicosis. At ADHB, Auckland, New Zealand, radioiodine dose is individualised by the prescribing physician according to patient characteristics. AimsWe investigated the outcomes of this approach. MethodsWe identified all patients receiving radioiodine for thyrotoxicosis at ADHB in 2015 and retrieved relevant clinical details. Results222 patients were prescribed radioiodine: 147 (66%) for Graves disease, 58 (26%) for toxic nodular goitre, and 17 (8%) for solitary toxic nodule. For Graves disease, 80% had one radioiodine dose (first dose median 550 MBq, range 200-1000 MBq; total dose 200-2400 MBq), 92% had the thyrotoxicosis cured, and 83% required thyroxine post-radioiodine. For toxic nodular goitre, 93% had one dose (median 550 MBq, range 400-1000 MBq, total dose 400-1800 MBq), 93% were cured and 22% required thyroxine. For solitary toxic nodule, all had one dose (median 550 MBq, range 500-550 MBq), all were cured and 35% required thyroxine. In 69/222 (31%) patients (35% of individuals with Graves disease, 17% with toxic nodular goitre, and 47% with solitary toxic nodule), the most recent TSH (mean 3.2 years post-radioiodine) was elevated (30% TSH >10 mu/L, 70% TSH 4-10 mu/L). ConclusionsFollowing radioiodine treatment, >90% of individuals have the thyrotoxicosis cured, but hypothyroidism is usual in Graves disease and occurs in 22-35% in toxic nodular goitre or solitary toxic nodule. Many individuals taking thyroxine after radioiodine have suboptimally controlled hypothyroidism.