Preservation of Echogenicity in Type II Amiodarone-Induced Thyrotoxicosis: Possible Histopathological Basis

Abstract

Sonographic hypoechogenicity of the thyroid in autoimmune and infective thyroiditis is well known (Fig. 1), whereas the sonographic appearance of type II amiodarone-induced thyrotoxicosis (AIT-II) has not been described. The ultrasound and scintigraphy findings of 16 consecutive patients diagnosed with AIT-II were reviewed. Thyroid echogenicity was normal in all patients (Fig. 2). Technetium-99m pertechnetate uptake was invariably reduced. AIT-II results from follicular damage and thyroid hormone leakage, a pathogenesis similar to subacute thyroiditis (SA). Subtle differences in histology defining the two conditions may explain the discrepant sonographic ap-