Thyroid iodine content measured by x-ray fluorescence in amiodarone-induced thyrotoxicosis: concise communication.

Iodine-induced thyrotoxicosis (liT) is characterized by (a) a low radioiodine uptake, increased by exogenous TSH, and (b) a spontaneous evolution towards cure within a few months. An hypothetical pathogenesis of liT is an initial inflation in the stores of thyroid hormones during iodine excess, followed by their sudden discharge into the circulation. Thyroid iodine content was measured by fluorescent scanning in 10 patients with amiodarone-induced thyrotoxicosis and in various control groups. Results were found to be high at the onset of the disease and to decrease during its course. The data agree with the hypothetical pathogenesis. Furthermore they may permit exclusion of a painless subacute thyroiditis, which is the main differential diagnosis of liT.