Successful Ablation of Lingual Thyroid Imaged with SPECT/CT and Treated with Radioactive Iodine-131 Avoiding Surgery and its Associated Risks

Objectives Lingual thyroid associated with thyroid agenesis is usually treated conservatively with levothyroxine replacement¹. Rarely, it becomes large enough, despite adequate thyroid stimulating hormone suppression, to cause obstructive or compressive symptoms². We report 3 patients with lingual thyroid who underwent successful ablation with radioactive iodine-131 (I-131) therapy.

Methods Three women presented to medical attention with symptoms of oropharyngeal obstruction (Table 1). Diagnostic iodine-123 (I-123) and technetium-99m (Tc-99m) scans performed with SPECT/CT demonstrated lingual thyroid, and absence of orthotopic functioning thyroid gland in all patients. The third patient had concurrent thyroglossal duct remnant. The patients elected to have radioiodine ablation of their lingual thyroid tissue. In preparation, levothyroxine was discontinued, and a low iodine diet was instituted. The third patient had the thyroglossal duct surgically removed. Therapeutic I-131 activity was determined based on thyroid tissue volume estimated on SPECT/CT and 24h lingual thyroid uptake according to the formula: calculated mCi of I-131 = (0.200 mCi/gram of target tissue x estimated grams) / uptake (%)

Results The patients were treated with 10.7, 17.5, and 15.4 mCi of I-131 respectively. There were no post-therapy complications. Six month thyroid scans revealed resolution of uptake in the lingual thyroid in two of the 3 patients. The first patient had complete resolution of obstructive symptoms, while the second patient had mild persistent globus sensation. In the third patient, a post-therapy scan 4 days following treatment demonstrated marked lingual thyroid uptake consistent with successful radioiodine targeting.

Conclusions We describe 3 patients in whom radioiodine treatment was used to successfully ablate lingual thyroid tissue with resolution or marked improvement in symptomatology, which in 2 patients obviated the need for surgery.