Endocrine Abstracts

Introduction: Amiodarone is an anti-arrhythmic drug rich in iodine compounds. One 200 mg tablet corresponds to about 25 times the daily requirement of iodine. One of the major complications of taking Amiodarone is the development of dysthyroidism which is observed in 15% to 20% of cases. Hyperthyroidism occurs in 1 and 13% of these patients.

Case report: We report the case of an 34 year old female patient, followed for complete arrhythmia by atrial fibrillation under Amiodarone 200 mg/d, who presented a thyrotoxicosis with TSH at 0.005 mUI/l, FT3 at 1.5 times normal and FT4 at 2 times normal. Anti-TPO and TSH receptor antibodies were negative. Cervical ultrasound showed an enlarged thyroid. Thyroid scintigraphy was white. Treatment with Carbimazole 40 mg/d and Prednisolone 60 mg/d was initiated without improvement. In view of the resistance to medical treatment, total thyroidectomy was indicated.

Discussion and conclusion: Amiodarone-induced hyperthyroidism can be explained by two mechanisms: thyroid hyperfunction by iodine overload in the context of a pre-existing nodular pathology (type 1) and must be treated with synthetic antithyroid drugs or thyroiditis with follicular destruction (type 2) and which responds well to glucocorticoids or the mixed form as in our patient’s case. Surgery is indicated if there is resistance to medical treatment, to correct thyrotoxicosis rapidly in patients for whom discontinuation of Amiodarone is not possible.

References: Bogazzi F, Bartalena L, Martino E. Approach to the Patient with Amiodarone-Induced Thyrotoxicosis. J Clin Endocrinol Metab 2010; 95 (6): 2529-2535