THE TOXIC EFFECTS OF SMALL IODINE SUPPLEMENTS IN PATIENTS WITH AUTONOMOUS THYROID NODULES

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Abstract
In 16 cases of toxic adenoma of the thyroid (autonomous hot nodule with complete suppression of the surrounding normal parenchyma) potassium iodide was given in doses of 100 .mu.g/day for 1 wk, 200 .mu.g/day for another and 400 .mu.g/day for a 3rd wk. There was a progressive increase in the serum T4 [thyroxine] level. Serum T3 [triiodothyronine] also increased, although this was significant only after the 1st wk. Serum TSH [thyroid stimulating hormone] was undetectable throughout the entire period of the study. This metabolic pattern is different from the response seen in cases of nontoxic endemic goiter, where small I supplements induce an increase in serum T4 but a decrease in serum T3. The present results may also explain the phenomenon of I-induced or I-precipitated hyperthyroidism (Jod-Basedow) when patients with autonomous thyroid are presented with a high I-intake. In contrast to the results obtained with small iodide doses, 2 other cases treated with large pharmacological doses of iodide showed a decrease in serum T4 and serum T3. The physician should be aware of the possibility of precipitating or aggravating thyrotoxicosis in patients with an autonomous hot nodule by increasing their intake of I.