POST I-131 THERAPY HYPERTHYROIDISM AND THYROID SWELLING RESULTING IN UPPER AIRWAY OBSTRUCTION IN A PATIENT TREATED FOR TOXIC MULTINODULAR GOITER

A CASE REPORT

Abstract

CASE
I-131 therapy is well-established as an efficient and safe treatment for hyperthyroidism. Complications such as post-therapy hyperthyroidism and thyroid swelling rarely occurred. We present a case of I-131 therapy-induced hyperthyroidism and thyroid swelling that resulted in upper airway obstruction in a patient treated for toxic multinodular goiter. (TNMG) A 63-year-old Thai female presented with a palpable thyroid mass. She had palpitations and mild dyspnea on exertion. Physical examination showed thyroid enlargement of approximately 60 grams with palpable multiple nodules of the right thyroid lobe and a single palpable nodule measuring 3-4 cm in the left thyroid lobe. Laboratory investigation showed FT4: 2.07 ng/dL (0.93-1.7) and TSH <0.01 uIU/mL (0.27-4.2). Thyroid ultrasound revealed multiple thyroid nodules with a maximum size of 4x3x6.3 cm (the right and left thyroid volume was 57 mL and 51mL, respectively). A thyroid scan revealed heterogeneously increased radiotracer uptake in the enlarged lobulated thyroid gland with multiple foci of relatively decreased and increased radiotracer uptake which were compatible with toxic multinodular goiter. She was diagnosed with TMNG and underwent 25 mCi of I-131. After 2 months of I-131 therapy, she came to the emergency department with dyspnea, palpitation, dysphagia, and thyroid enlargement. Physical examination revealed an increased size of the thyroid gland, approximately 80 grams, with an inspiratory stridor. Laboratory investigation showed FT3: 13.41 pg/ml (1.6-4), FT4: 2.35 ng / dL (0.7-1.48) and antiTSH-R: 33.42 IU/L (0-1.75). The chest film and computed tomography showed a narrowing of the tracheal lumen (4 mm in diameter). Furthermore, her serum calcium was 11.6 mg/dL (8.5-10.5), phosphate was 3 mg/dL (2.3-4.7), and iPTH was 130 pg/mL (15-65). A parathyroid MIBI scan was done which revealed a 0.9 x 1.1 cm nonMIBI avid nodule located at the upper pole of the left thyroid lobe, suspected for a parathyroid adenoma. She was diagnosed with post-I-131 therapy hyperthyroidism that caused upper airway obstruction concomitant with primary hyperparathyroidism. She was admitted to the intensive care unit and treated with propylthiouracil, dexamethasone, and propranolol. Subsequently, she underwent total thyroidectomy with left upper and lower parathyroidectomy, resulting in an improvement in her symptoms.

Our patient developed rebound hyperthyroidism with swelling of the thyroid after the I-131 treatment for 2 months, which resulted in impending upper airways. The present case highlights the need for physicians to be aware that rebound hyperthyroidism may present later than usual and may also cause thyroid swelling in some cases.