Endocrine Abstracts

Introduction: Radioiodine (131-I) treatment for benign thyroid disease has a 70 year history. Among the radioactive isotopes, (131-I) can be used successfully. The intention of radioiodine treatment is primarily to induce a euthyroid or hypothyroid state, but in the case of large multinodular goitres, shrinkage represents a secondary aim of therapy. The optimal method for determining iodine-131 treatment doses for Toxic Thyroid nodule is unknown, and techniques have varied from a fixed dose to more elaborate calculations based upon gland size, iodine uptake, and iodine turnover. Historically, UK prescribing has varied widely according to local custom and practice. The range of activities currently prescribed varies between 200–800 mega Becquerel (MBq), with the majority of patients receiving 400–600 MBq. Toxic adenoma, usually mild hyperthyroidism required 500 MBq of 131-I radioiodine.

Data/Method: We collected data from nuclear medicine department and hospital electronic and paper patient records. In this retrospective audit we had total 10 patients (8-female and 2 male) who received a single fixed dose radioiodine (131-I) for autonomous toxic thyroid nodule in the 10-year period from 2007–2016. Patients’ age were between 20 to 75 years. All patients had suppressed TSH at<0.05 nmol/l, with mildly raised thyroid hormones, and thyroid antibodies (TPO and TR) were negative which tended to excluded thyroid immune disorders.

Results: We checked their Thyroid function tests at 3, 6, 12 and 24 -month periods. There were significant improvements in thyroid function tests, with 4/10 patients achieving results within the euthyroid range and 6 patients becoming hypothyroid. All nodules shrank down to become non-palpable and no patient required a repeated dose of 131-I.

Recommendations: Though, 500MBq of 131-I radioiodine is recommended for toxic thyroid adenoma in the UK, our data showed that a smaller fixed dose is 100% effective and probably associated with lower rate of hypothyroidism (60%) at 2 years. Ref; Radioiodine in the management of benign thyroid disease Clinical guidelines, Royal College of Physicians, UK.