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—Dr Daniels is correct to point out that a low dose of levothyroxine can produce thyrotoxicosis in the presence of autonomous thyroid tissue. As stated in the figure legend in our article, the patient had not been receiving levothyroxine therapy three weeks before the preoperative sodium iodide I 123 thyroid scan. Several weeks later, the patient became clinically mildly hyperthyroid, with a serum thyroxine uptake of 16.0 μg/dL. At that time, she had not received any levothyroxine therapy for six weeks. Nevertheless, the indication for surgery was not the mild hyperthyroidism, but the mass effect of the enlarged left thyroid gland, which was causing a pressure sensation in the patient's neck.Potassium iodide in pharmacologic doses has been used for many years to prepare thyrotoxic patients for surgery. In addition to producing a prompt block to thyroid hormone secretion, iodide decreases vascularity within 14 days,1 making the