Amiodarone-Induced Thyrotoxicosis and Clinical Risk Factors for Thyrotoxic Crisis

Background Amiodarone-induced thyrotoxicosis (AIT) is a serious complication of long-term amiodarone therapy. Its most severe manifestation is thyrotoxic crisis (TxC), a rare but life-threatening condition associated with high morbidity and mortality. Aim To analyze patients with AIT, identify demographic and clinical parameters, evaluate diagnostic and therapeutic approaches, and determine predictive risk factors for TxC. Methods A retrospective study of 55 consecutive patients with confirmed AIT followed between 2005 and 2024. Baseline characteristics, laboratory findings, thyroid ultrasound, clinical presentation, therapy and outcomes were analyzed. Patients were classified into AIT type I, type II, or mixed type. TxC was diagnosed using the Burch–Wartofsky scoring system. Results The cohort included 45 men (82%) and 10 women (18%), mean age 62.3 ± 9.9 years. Amiodarone was prescribed mainly for atrial fibrillation (78%). Mean duration of therapy until AIT onset was 988 ± 502 days. At diagnosis, mean fT4 was 43.2 ± 18.3 pmol/L and mean TSH 0.017 ± 0.052 mIU/L. Thyroid volume averaged 18.1 ± 8.7 mL, and goiter was present in 47% of patients. AIT types were distributed as follows: type I in 23%, type II in 44%, and mixed type in 33%. Six patients (11%) developed TxC, all men, with higher maximum fT4 (> 74.5 pmol/L), larger thyroid volume (> 19 mL), and more frequent atrial fibrillation with rapid ventricular response. Urgent thyroidectomy was required in 5 of 6 cases with TxC. Conclusion AIT is a clinically important complication of amiodarone therapy. Male sex, younger age, large thyroid volume, high maximum fT4, mixed AIT type, and cardiac decompensation are supposed clinical risk factors for TxC. Early recognition and interdisciplinary management are crucial to improve outcomes.