Endocrine Abstracts

Introduction: Hyperthyroidism owing to Graves’ disease or toxic nodular goiter is a common condition seen in clinical practice. The available modes of therapy are antithyroid drugs, surgery and radioiodine (RAI) therapy. Radioiodine is an effective, safe and relatively inexpensive form of therapy in patients suffering from hyperthyroidism. The aim of our study is to assess the effectiveness of radioactive iodine (RAI) treatment in patients with hyperthyroidism.

Methods: We retrospectively analyzed 70 patients suffering from hyperthyroidism and receiving RAI treatment. They were diagnosed as having hyperthyroidism based on clinical symptoms, elevated thyroid hormone levels and suppressed thyroid-stimulating hormone levels.

Results: The mean age of the study population was 38.33±13.11 years. Forty-seven patients were female (67.1%) and 23 were male (32.9%). Sixty-five percent had Graves ‘disease, 32% had toxic multinodular goiter and 3% had toxic single nodule. Sixty-five percent had been pre-treated with anti-thyroid medications. The mean duration of follow-up was 25.14±14.25 months. The average dose of I131 used for therapy in our patients was 14.15±0.34 mCi. Mean serum levels of free thyroid hormones were significantly lower in patients with toxic multinodular goiter compared to patients with Graves’ disease (38.2 vs 58.6 pmol/l, P=0.04). Mean thyroid volume, as assessed by ultrasonography, was larger in patients with toxic multinodular goiter than in patients with Graves’ disease (61.2 vs 24.2 ml, P<0.01). Patients with toxic multinodular goiter received a significantly higher dose of iodine than patients with Graves’ disease (14.2 vs 12.3 mCi, P<0.01). The incidence of hypothyroidism was 52% at 6 months and 61% at one year. The response rate was significantly higher in the group without pre-treatment with anti-thyroid medications.The levels of serum thyroid hormone at presentation were correlated with the development of hypothyroidism after RAI treatment.

Conclusion: Radioactive iodine treatment is an effective modality for definitive treatment of hyperthyroidism. Response rate was not related to gender, etiology or RAI dosage. Pre-treatment with anti-thyroid medication reduces the response rate.