To the Editor.—
E.D. Luby and his collaborators (218:1298, 1971) present an interesting observation. The mild antithyroid effect of lithium is well-known, although the mechanism of its action is incompletely understood. A goiter developed or increased in twelve of 330 patients in one series, but all remained clinically euthyroid.1 In another Danish study, serum protein-bound iodine level was significantly decreased after one week of lithium treatment,2 but there was a tendency toward control levels after some weeks.Dr. Luby's patient appears to be the first to become clinically hypothyroid during lithium treatment. Interestingly, this patient received an iodine-containing drug in addition to large doses of lithium carbonate during the month preceding the appearance of clinical signs of hypothyroidism. This drug, isopropamide iodide, has an iodine content of 26%; as the daily dose was 4 mg, it will have added 1 mg/day of iodine to the dietary iodine
Wiener JD. Lithium Carbonate-Induced Myxedema. JAMA. 1972;220(4):587. doi:10.1001/jama.1972.03200040099033
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