Iodine-induced hypothyroidism and its effect on the severity of asthma.

Among 1107 patients with asthma or chronic asthmatic bronchitis and 96 with hypothyroidism we found 12 patients with both diseases. Seven of these patients had hypothyroidism induced by iodine-containing expectorants. Five of 209 patients with hyperthyroidism had coexistent asthmatic lung disease, but none of these five had been taking iodine. The severity of asthma is considered in relation to changes in thyroid function following withdrawal of iodine. Three patients had an exacerbation of their asthma, while another three had no change in their asthma when the iodine treatment was discontinued and the euthyroid state subsequently restored. All six patients had a marked improvement of their general wellbeing when the euthyroid state was re-established. It is concluded that treatment with iodine-containing expectorants causing hypothyroidism is unwise and should be withdrawn even when the patients praise the beneficial effect of iodine on the asthma per se.