Endocrine Abstracts

Introduction: Thyroid storm is a rare medical emergency with high mortality, which usually results from acute exacerbation of hyperthyroidism. Amiodarone is a highly used class III antiarrhythmic drug and amiodarone-induced thyrotoxicosis is an infrequent effect of this medication, whose treatment may be difficult.

Case study: A 20-year old male with congenital cardiomyopathy (Fallot tetralogy and Ebstein anomaly), chronically medicated with amiodarone 200 mg/day since age 2, was admitted to the emergency room with palpitations, diaphoresis, nausea, vomiting and diarrhea. EKG showed atrial fibrillation with rapid ventricular response (HR 160 bpm). Blood analysis showed hyperthyroidism – TSH <0.005 μUI/ml; FT₃ 7.83 pg/ml (2.57–4.43) and FT₄ 5.50 ng/dl (0.93–1.70). Burch-Wartofsky’s score was 55. He started tiamazol 30 mg/day and prednisolone 40 mg/day, but because of his cardiac disease, amiodarone could not be withdrawn. Despite adequate treatment, there was no clinical response and patient remained hypotensive, taquicardic and at risk of cardiogenic shock. Potassium perchlorate was initiated at 400 mg 8/8 h with subsequent normalization of heart rate and hemodynamic stability. He was discharged after radiofrequency ablation of an abnormal signal pathway with EKC in sinus rhythm and amiodarone was suspended. Thyroid ultrasound showed thyroid goiter (24.5 ml) with heterogeneous structure. There was a lack of 99 mTc uptake in scintigraphy (0.5%). Normalization of hormones was reached after eight months of onset of the disease, with tiamazol 70 mg/day and prednisolone 20 mg/day.

Conclusions: Amiodarone-induced thyrotoxicosis occurs in 5–10% of patients and may cause significant morbidity, especially in patients with significant cardiac disease and when it cannot be discontinued. Differential diagnosis between type 1 and type 2 is not always easy and sometimes mixed forms occur, adding more challenges and difficulty to the treatment, particularly when antithyroid drugs and corticosteroids are ineffective.