Comparison of Different Doses of 131I in Severe Graves' Hyperthyroidism

Graves' disease (GD) is the most frequent cause of hyperthyroidism, affecting mainly women aged 40-60 years. Radioiodine (¹³¹I), introduced in 1941, has become a cornerstone in the treatment of GD hyperthyroidism. Because of its safety, low costs and rapid effect, it is considered a first line therapy in the United States. However, treatment failure occurs in about 15-25% of patients treated with radioiodine. Patients not cured with the first dose of radioiodine usually present severe hyperthyroidism, characterized by large goiter, high 24-hour radioiodine uptake (24h-RAIU) and very high levels of thyroid hormones. We have previously shown that large goiter (≥48ml) is an independent predictor of treatment failure. In these patients, the therapeutic failure was 40.0% while in patients with smaller goiter was only 6.5% (P=0.005; unpublished). It is generally accepted that higher doses of radioiodine improves cure rates. Indeed, a recent meta-analysis found a correlation between radioiodine dose and therapeutic success in GD patients. To our knowledge, there are no published studies evaluating cure rates with different radioiodine doses in severe GD.

Inclusion criteria

• Consecutive patients with a recent diagnosis of Graves' disease and goiter ≥ 48 ml, attending the Endocrine Division at Hospital de Clinicas de Porto Alegre are eligible.

Exclusion criteria

• Patients with previous treatment with radioiodine or thyroidectomy,
• Signs of moderate or severe ophthalmopathy (proptosis > 22 mm, ophthalmoplegia, chemosis, or lagophthalmos),
• Severe heart disease (symptomatic coronary heart disease, class III heart failure, New York Heart Association criteria),
• Debilitating conditions, and
• Large and compressive goiters (> 150 g).