Context: Hashimoto's thyroiditis is an autoimmune disease which can produce marked clinical symptoms when patients have large diffuse goiters.

Design: This retrospective cohort study was designed to evaluate whether radioactive iodine (RAI) is effective for Hashimoto's thyroiditis with a large goiter. Starting in November 1999, 13 Hashimoto's patients, with large goiters, whose thyroiditis was refractory to TSH (TSH) suppression therapy with thyroid hormone administration, 2 men and 11 women with a mean age of 61.2 ± 8.9 yr (50-79 yr), were recruited for the present study. The duration of symptomatic goiter before undergoing RAI was 12.0 ± 7.9 yr (4-33 yr). Thirteen mCi of ¹³¹I was administered 2 to 6 times, at an interval of 1 to 6 months on an outpatient basis. Thyroid weight was measured ultrasonographically, or by CT if ultrasound was not possible due to the large size of the goiter.

Results: RAI was administered an average of 4.7 ± 1.4 times (2-6 times), with a total dose of 59.8 ± 17.3 mCi (25.0-78.0 mCi). The observation period was 47.9 ± 13.4 months (26-66 months) after the first RAI. The average weight of the thyroid gland was 125.3 ± 57.7 g (42.9-269.4 g) before the first RAI, decreasing significantly to 49.7 ± 25.8 g (18.3-93.3 g) after the last RAI (P < 0.001, paired Student's t test). The percent reduction from baseline was 58.7 ± 14.2% (35.7-84.0%). None of the patients showed an increase in goiter size or complained of a pressure sensation after any of the RAI treatments.

Conclusion: RAI is effective in Hashimoto's thyroiditis with a large goiter.