Cardiovascular Outcomes, Hospitalization, and Mortality following Amiodarone-Induced Thyrotoxicosis

Amiodarone-induced thyrotoxicosis is a recognized adverse effect of amiodarone therapy. However, its long-term effects on cardiovascular morbidity, hospitalization, and mortality remain insufficiently characterized.

The objective of this study is to evaluate the incidence of cardiovascular events, hospitalizations, and all-cause mortality following amiodarone-induced thyrotoxicosis and to assess their association with clinical, biochemical, and therapeutic parameters.

A retrospective cohort study was conducted including 113 adult patients diagnosed with amiodarone-induced thyrotoxicosis and followed at a tertiary endocrinology center between 2008 and 2024. Clinical and biochemical characteristics, therapeutic interventions, cardiovascular events, hospital admissions, and mortality were recorded. The event-free survival was evaluated using Kaplan-Meier curves, and predictors of outcomes were assessed using Cox proportional hazard regression models.

Fifty patients (44.2%) were classified as amiodarone-induced thyrotoxicosis type 1 and 63 patients (55.8%) as amiodarone-induced thyrotoxicosis type 2. Over a median follow-up of 52 months, 42.5% experienced at least one cardiovascular event, 38.0% required hospitalization, and 33.6% died. Serum free thyroxine levels at diagnosis were significantly higher in patients who developed cardiovascular events (hazard ratio: 2.6; 95% confidence interval: 1.9-3.7 vs. hazard ratio: 2.3; 95% confidence interval: 1.6-3.4 ng/dL; p=0.042). Kaplan-Meier analysis showed reduced survival in older patients (p<0.001). In the multivariate model, age at diagnosis was the only independent predictor of mortality (hazard ratio=1.06; 95% confidence interval: 1.02-1.10; p=0.001). Neither amiodarone-induced thyrotoxicosis type nor treatment intensity were significantly associated with cardiovascular outcomes, hospitalization, or survival.

Amiodarone-induced thyrotoxicosis is associated with substantial long-term clinical burden. In unadjusted analysis, elevated free thyroxine levels were associated with cardiovascular events, although this association did not reach significance after multivariate adjustment. Age at amiodarone-induced thyrotoxicosis diagnosis was the only independent predictor of mortality. Amiodarone-induced thyrotoxicosis type and treatment intensity did not significantly influence outcomes.