Amiodarone-Induced Thyrotoxicosis After Total Thyroidectomy for Metastatic Follicular Thyroid Cancer

Abstract

Objective: To describe the case of a man who developed amiodarone-induced thyrotoxicosis (AIT) after a total thyroidectomy for metastatic follicular thyroid cancer because of the effect of the drug on metastasis. To the best of our knowledge this is the first reported case of this condition. Methods: We completed a retrospective review of medical records and laboratory results including thyroid function tests as well as imaging reports including plain radiographs, positron emission tomographs, computed tomographs, and histology reports. Results: A 78-year-old man had undergone a total thyroidectomy for follicular thyroid cancer. He had meta-static disease in his chest and vertebrae, and after the operation he was started on suppressive levothyroxine treatment prior to ablative radioactive iodine treatment. Prior to thyroidectomy, his thyroid-stimulating hormone (TSH) concentration was 3.21 mU/L (reference range is 0.35 to 3.50 mU/L). On suppressive thyroxine replacement, his TSH concentration was 0.02 mU/L, his free thyroxine was 13 pmol/L (reference range is 8 to 12 pmol/L), and free triiodothyronine was 5.8 pmol/L (reference range is 3.8 to 6.0 pmol/L). He subsequently had a myocardial infarction and required antiarrhythmic treatment with amiodarone. Eleven days later he developed the clinical and biochemical features of thyrotoxicosis (TSH <0.01 mU/L, free thyroxine of 41 pmol/L, and free triiodothyronine of 14.7 pmol/L). His thyroxine dose was reduced and then discontinued 3 days later. AIT was the principal differential diagnosis, but before being able to determine the nature of the condition he died 18 days after his myocardial infarction. Conclusion: AIT can still occur after total thyroidectomy if metastatic tissue is present.

Mixed medullary—papillary thyroid carcinoma with mixed lymph node metastases: A case report

“…With regard to treatment with amiodarone, AIT can be found in 3% to 12% of patients who take this drug 27 ; however, the presence of thyroid cancer in thyroidectomy specimens removed for AIT is rare, 2832 In recent years, several case reports have raised the possibility of an association between amiodarone and cancer 36,37 . Thyroid dysfunction resulting from the administration of amiodarone can be induced in patients with previous thyroid carcinoma, 38 or it can be manifested after the introduction of this drug 39 . Even though our patient had been evaluated by another hospital for AIT and we were given access to a few details regarding his etiological assessment and approach, as far as we know, this is the first time that a case of mixed thyroid carcinoma has been reported in patients being treated with amiodarone.…”