Endocrine Abstracts (2007) 13 P319

Retrospective analysis of radioiodine therapy for thyrotoxicosis with a 550Mbq dose

Ambar Basu, Kalpana Kaushal, Jonathan Hill & Simon J Howell


Royal Preston Hospital, Preston, Lancashire, United Kingdom.


Background: Radioiodine therapy using I131 is a well established, safe, cheap and effective treatment for thyrotoxicosis. Current recommendations support the administration of 400-550 Mbq. At this centre, we use a dose of 550 Mbq with the aim of minimising the chance of the patient remaining thyrotoxic following therapy.

Aims: To determine (a) the thyroid status of patients following treatment with I131 at a dose of 550 Mbq, (b) the speed of onset of hypothyroidism, and (c) the influence of various baseline parameters on the outcome.

Methods: Retrospective audit of patients receiving radioiodine treatment for thyrotoxicosis between 2002 and 2006 at our centre.

Results: Records from 92 patients (75% female), median age 55 years (range 18–89) were examined. Median radioiodine dose 527 Mbq (range 440–560); median duration of first follow-up was 7.5 weeks (range 2–24 weeks). 30(32.6%) had a diagnosis of Graves disease, 34(37%) toxic multinodular goitre and in the remaining 28 (20.4%) the underlying aetiology was unclear. After radioiodine therapy 11(12%) were euthyroid, 1 remained hyperthyroid and was lost to follow up, and 5(5.4%) patients remained thyrotoxic and required a second dose of radioiodine. Of these 5 patients 4 had a diagnosis of Graves disease and 1 had undefined thyrotoxicosis. The remaining 75(81.5%) became hypothyroid. The majority(70%) were diagnosed with hypothyroidism in the first 16 weeks after therapy, of whom 34% were hypothyroid by 8 weeks and a further 21% by 12 weeks. Patients who remained thyrotoxic following radioiodine had significantly higher FT4 at diagnosis than those who were euthyroid or hypothyroid after therapy (74.8 pmol/L vs. 39.7 pmol/L vs. 38 pmol/L P<0.001). There was no significant effect of age,sex or prior medical treatment on the outcome.

Conclusion: Radioiodine administered at a dose of 550 Mbq is effective for the treatment of thyrotoxicosis. Hypothyroidism is common and in the majority of cases occurs within the first 16 weeks of administration of radioiodine.

Article tools

My recent searches

No recent searches.