Endocrine Abstracts

Introduction: Amiodarone is a widely used agent for life-threatening arrhythmias. Although amiodarone is associated with few side effects, including thyroid dysfunction in 15-20% of patients. Amiodarone-induced thyrotoxicosis (AIT) is a major adverse effect that can cause recurrence of arrhythmias and exacerbation of heart failure. It is a challenging diagnosis that affects 0,003% to 10 % of patients taking amiodarone. Type I AIT is seen in patients with preexisting thyroid disease and is generally treated with thionamides, while type II AIT represents a destructive thyroiditis that responds to glucocorticoids. A mixed type exists and is associated with higher mortality, especially in older adults with cardiovascular disease. Thyroidectomy is considered the last resort option for patients intolerant or refractory to medical treatment.

Case report: We present a case of 78-year-old women with a history of atrial fibrillation, essential hypertension and heart failure. She was referred to our hospital because of heart failure exacerbation. Laboratory tests showed suppressed TSH and high level of FT4 and FT3. She endorsed palpitations, excessive sweating, and reported taking amiodarone for 3 years prior to presentation. Thyroid autoantibodies were negative. Thyroid ultrasound showed mild thyromegaly with multiple nodules and normal vascularity. Mixed type AIT was suspected and she was started on methimazole 20 mg and methylprednisolone 32 mg daily. Patient was discharged with improved thyroid hormone results and continued on the same dose of methimazole and steroid. On a follow-up visit after four weeks, thyroid hormones were still on toxic levels. Patient started showing adverse effects of prolonged corticosteroid and methimazole therapy, namely a difficult to control diabetes mellitus, corticosteroid-induced myopathy and hepatotoxicity. She remained thyrotoxic despite using higher doses of methylprednisolone and methimazole without improvement in overall status. Several days after admission, a total thyroidectomy was performed resulting in significant clinical and laboratory improvement and the patient was safely discharged.

Conclusion: This case illustrates the potentially severe consequences of therapeutic medications and the importance of close surveillance of the side effects in several organs. Most cases of AIT are amenable to medical therapy with thionamides and/or glucocorticoids. In the minority of patients who do not respond to these measures or are too critically ill thyroidectomy is a viable option.

Fonseca M, Ferreira M, Paulo J, Neves Z. A Refractory Case of Amiodarone Thyrotoxicosis. Cureus. 2022 Aug 29;14(8):e28527. doi: 10.7759/cureus.28527. PMID: 36185869; PMCID: PMC9516872.