Endocrine Abstracts

Methods: We retrospectively reviewed the medical notes of 39 patients who received radioiodine treatment (RAI) for thyrotoxicosis from 2004 until February 2010. Only 5.1% of patients had history of partial thyroidectomy; patients with previous history of RAI for thyrotoxicosis were excluded. All patients received written information leaflet for RAI.

Results: Thirty (76.9%) patients were females and the median age of diagnosis was 59.5 years. 97.4% were Caucasian; 17.9% had positive family history of thyrotoxicosis; current smokers (31%), ex-smokers (18%); 7.7% had taken Amiodarone or Lithium in the past; Graves’ disease (56.4%), Multinodular goitre (41%), and unspecified diagnosis (2.6%). Other co-morbidities included diabetes (25.6%), hypertension (35.9%), atrial fibrillation (10.2%) and no heart failure. These patients were followed up in the endocrine clinic post RAI at (mean 11.5 weeks, median 9 weeks); hypothyroidism was diagnosed at (mean 26.3 weeks, median 11 weeks) and Thyroxine dose post-RAI (mean 93.2 mcg, median 100mcg daily) was recorded. 69.2% became hypothyroid post-RAI, euthyroid (20.5%) while 10.3% had further relapse of thyrotoxicosis and required a second dose of RAI. All patients achieved cure after second dose of RAI. One patient experienced radiation thyroiditis, while another one experienced pruritis post RAI. Incidence of hypothyroidism following RAI was 48.6% (3 months), 54.1% (6 months), 59.4% (9 and 12 months) and 64.9% (24 months). This is also consistent with literature with studies showing that 50%–60% of patients receiving high dose RAI (more than 370 MBq) develop hypothyroidism within one year followed by a further annual incidence of 2%–3%.

Conclusion: RAI treatment is highly effective in treating hyperthyroidism with cure rate approaching 90%. However, a significant proportion of patients develop hypothyroidism within one year, suggesting the need for close monitoring to ensure adequate thyroxine replacement.

Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.