To the Editor.—
The occurrence of transient hypothyroidism one to four months after treatment with radioactive iodine (131I) for toxic diffuse goiter (TDG), although rare, has been described.1-4 Previous studies have failed to identify any laboratory or clinical measure that would predict whether the hypothyroidism induced by131I would prove to be transient or permanent. To evaluate this question, we compared four patients with transient hypothyroidism to 23 patients who developed permanent hypothyroidism within four months of radioactive iodine therapy for TDG.
Patients and Methods.—
During the past year, 27 of 36 (75%) patients who had received 10 mCi of sodium iodide I 131 for TDG became hypothyroid within four months of therapy. These results are similar to those of other series.5 Seventeen patients developed clinical hypothyroidism with low thyroxine (T4) and triiodothyronine (T3) levels and elevated thyrotropin (TSH) levels. In addition to the