EFFECT OF SMALL DOSES OF IODINE ON THYROID-FUNCTION IN PATIENTS WITH HASHIMOTOS-THYROIDITIS RESIDING IN AN AREA OF MILD IODINE DEFICIENCY

Objective: Several studies have suggested that iodine may influence th yroid hormone status, and perhaps antibody production, in patients wit h autoimmune thyroid disease. To date, studies have been carried out u sing large amounts of iodine. Therefore, we evaluated the effect of sm all doses of iodine on thyroid function and thyroid antibody levels in euthyroid patients with Hashimoto's thyroiditis who were living in an area of mild dietary iodine deficiency. Methods: Forty patients who t ested positive for anti-thyroid (TPO) antibodies or with a moderate to severe hypoechogenic pattern on ultrasound received 250 mu g potassiu m iodide daily for 4 months (range 2-13 months). An additional 43 pati ents positive for TPO antibodies or with hypoechogenicity on ultrasoun d served as a control group. All patients were TBII negative. Results: Seven patients in the iodine-treated group developed subclinical hypo thyroidism and one patient became hypothyroid. Three of the seven who were subclinically hypothyroid became euthyroid again when iodine trea tment was stopped. One patient developed hyperthyroidism with a concom itant increase in TBII titre to 17 U/l, but after iodine withdrawal th is patient became euthyroid again. Only one patient in the control gro up developed subclinical hypothyroidism during the same time period. A ll nine patients who developed thyroid dysfunction had reduced echogen icity on ultrasound. Four of the eight patients who developed subclini cal hypothyroidism had TSH concentrations greater than 3 mU/l. In 32 p atients in the iodine-treated group and 42 in the control group, no si gnificant changes in thyroid function, antibody titres or thyroid Volu me were observed. Conclusions: Small amounts of supplementary iodine ( 250 mu g) cause slight but significant changes in thyroid hormone func tion in predisposed individuals.