Endocrine Abstracts

We reviewed the outcomes of 40 patients (30F, 10M; mean age 56 years) with thyrotoxicosis who were referred for radioactive iodine treatment (RAI) via our department (catchment area of 130 000 people) over a period of 3 years (February 2004–March 2007). Twenty-three patients had Graves (GD); 6 had single toxic adenoma (STA); 11 had toxic multinodular goitre (MNG). Thirty-six patients (90%) had a preceding isotope scan, and 2 patients (5%) had previous partial thyroidectomy. Duration with anti-thyroid treatment (ATD) prior to RAI was as follows: <3 m (12% of patients), 3–6m (18%), and more than 6 m (60%) and no preceding ATD (10%). Carbimazole was the ATD used in 83% of patients receiving prior treatment.

Outcome post RAI: About 77% of patients achieved remission from thyrotoxicosis after a single dose (472 MBq for Graves, 689 for MNG, 567 for STA). Remission rate after single treatment per RAI dose as follows: 77% for dose <450 MBq, 74% for dose 450–750 MBq, and 100% for dose above 750 MBq. Remission rate after first dose per diagnosis was 70% for GD, 80% for MNG and 100% for STA. Prior ATD therapy with Carbimazole or Propylthiouracil or no ATD was associated with remission in 77%, 67%, and 100% retrospectively.

About 56% developing permanent hypothyroidism after initial dose, requiring replacement (71% after second dose). The average time to develop hypothyroidism was 3.5 months. Remission rate was independent of TSH levels immediately prior to RAI. About 15% required a second RAI dose and only one patient needed a third dose. About 90% of patients had thyroid function checked within 6 weeks of RAI

In conclusion, RAI is effective treatment in thyrotoxicosis; however, it is associated with high rate of hypothyroidism, and a smaller rate of failure. GD patients appear more RAI resistant. Our patients are closely followed up post treatment as per recommendations.