A 54-year-old woman comes to the emergency department with palpitations. She has experienced paroxysmal atrial fibrillation for the past 6 months. She has had extensive investigations for an underlying cause, including echocardiography and thyroid function testing, which were normal. The patient was started on amiodarone 6 weeks ago by her cardiologist and did well in the interim. She has had no change in her weight or intolerance to hot or cold temperatures. Her other medications include atenolol and low-dose aspirin. On physical examination, the patient appears comfortable. Her blood pressure is 132/82 mm Hg and heart rate is 112/min and irregular. Laboratory studies show a normal complete blood count and basic metabolic panel. ECG shows atrial fibrillation with rapid ventricular response. Thyroid function markers are as follows: What is the best management for this patient?

Question

A 54-year-old woman comes to the emergency department with palpitations.  She has experienced paroxysmal atrial fibrillation for the past 6 months.  She has had extensive investigations for an underlying cause, including echocardiography and thyroid function testing, which were normal.  The patient was started on amiodarone 6 weeks ago by her cardiologist and did well in the interim.  She has had no change in her weight or intolerance to hot or cold temperatures.  Her other medications include atenolol and low-dose aspirin.  On physical examination, the patient appears comfortable.  Her blood pressure is 132/82 mm Hg and heart rate is 112/min and irregular.  Laboratory studies show a normal complete blood count and basic metabolic panel.  ECG shows atrial fibrillation with rapid ventricular response.  Thyroid function markers are as follows:  What is the best management for this patient?

Quizplus · Accepted Answer

Explanation: Amiodarone decreases the peripheral conversion of T4 to T3, with abnormalities in thyroid biomarkers (normal to high TSH, low T3, high T4) seen within the first 3 months of therapy. These abnormalities then improve over the subsequent 3-6 months. Patients are usually clinically euthyroid, and no treatment is necessary. (Choice A) The half-life of amiodarone is more than 100 days. Consequently, discontinuation will not improve thyroid dysfunction in a short period. However, amiodarone may be continued safely with close follow-up in euthyroid patients. (Choice B) Amiodarone-induced destructive thyroiditis with thyrotoxicosis is treated with glucocorticoids. (Choices C and D) Levothyroxine is the treatment of choice for amiodarone-induced hypothyroidism. Relatively high doses of levothyroxine may be required in amiodarone-induced hypothyroidism due to amiodarone's effect of decreasing the conversion of T4 to its active form, T3. Combination treatment with levothyroxine and liothyronine is not shown to be superior to levothyroxine alone. Educational objective: Amiodarone-induced biochemical abnormalities in thyroid hormone metabolism improve with time, and no treatment is necessary. References: Amiodarone and thyroid dysfunction. (http://www.ncbi.nlm.nih.gov/pubmed/20689491)

A 54-Year-Old Woman Comes to the Emergency Department with Palpitations