Endocrine Abstracts

Introduction: In the interpretation of the thyroid tests in a patient treated chronically with amiodarone (AMD), the effects on the thyroid should be considered. The aim of the study was to evaluate the thyroid parameters in amiodarone-induced thyrotoxicosis (AIT), compared to endogenous hyperthyroidism.

Materials and methods: The study group included 36 patients with AIT (mean age 57.6±7.8 years, 11 women (F), 25 men (M)). The mean duration of AMD-treatment was 26.3±16.4 months. The cases were classified as follows: 10 with type 1 AIT, 13 with type 2, and 13 with mixed type. The control group included 39 patients (F:M, 14:25), with clinical endogenous hyperthyroidism. For type 1 AIT, the control group included: 24 cases with Graves’disease, 2 patients with toxic adenomas, one multinodular goiter, and for type 2 AIT, the control cases were 13 patients with subacute thyroiditis in thyrotoxic phase. The diagnosis was confirmed by a suppressed value of serum TSH (<0.1 mUI/l), associated with high levels of FT₃ and/or FT₄.

Results: The patients with type 1 AIT presented lower thyroid volumes than the controls (30±8.2 vs 34.7±12.3 ml, P=0.27), while the type 2 cases presented similar volumes with controls (18.6±5.5 and 17.9±4.1 ml, P=0.74). AIT patients presented lower values of serum TSH (0.009±0.013 mU/l) than the controls (0.021±0.037 mU/l, P=0.067), although there were no differences among the subtypes of AIT. Mean thyroxine levels were higher in AIT group than the controls (4.48±1.6 and 4.08±1.53 ng/dl, P=0.29). FT₃ presented significantly lower values in type 1 AIT (6.62±1.85 pg/ml), than the controls (10.7±5.4 pg/ml, P=0.02), while in type 2, it showed similar concentrations (6.2±2.86 vs 7.2±3.77 pg/ml, P=0.53).

Conclusion: AIT presents a specific hormonal profile, which reflects the effects of AMD on thyroid hormones metabolism: significantly lower FT₃ (P=0.01) and higher FT₄ values (P=0.29), as compared to endogenous hyperthyroidism.