Differentiation between the two types of amiodarone-associated thyrotoxicosis using duplex and amplitude Doppler sonography.

PURPOSE To evaluate the usefulness of Doppler parameters in the differentiation between the two types of amiodarone-associated thyrotoxicosis (AAT). MATERIAL AND METHODS One hundred thirty-seven individuals were selected at our institution. They were divided into four groups: 84 normal subjects (N), 30 euthyroids taking amiodarone (A), 14 AAT type 1 patients (AAT1), and nine AAT type 2 patients (AAT2). Each AAT type was classified according to (131)I uptake and clinical outcome. Blindly, the resistance and pulsatility indexes (RI, PI), systolic peak velocity, and color pixel density (CPD) were calculated. RESULTS AAT1 had greater CPD than AAT2 (P = 0.02). The latter group had similar vascularization to the N and A groups (P = 0.45). The area under the receiver operating characteristic (ROC) curve showed that systolic peak velocity in the inferior thyroid arteries and CPD were the best parameters in the differentiation between AAT type 1 and AAT type 2 (Az = 0.83 and 0.84, respectively). Impedance indexes were useless. CONCLUSION Our results demonstrate that objective tests such as systolic peak velocities in the thyroid arteries and CPD are reliable parameters for differentiating between the two types of AAT.