Effect of small doses of iodine on thyroid function in patients with Hashimoto's thyroiditis residing in an area of mild iodine deficiency

in European Journal of Endocrinology
Authors:
W ReinhardtDepartment of Medicine, University of Essen, Germany.

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M LusterDepartment of Medicine, University of Essen, Germany.

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KH RudorffDepartment of Medicine, University of Essen, Germany.

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C HeckmannDepartment of Medicine, University of Essen, Germany.

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S PetraschDepartment of Medicine, University of Essen, Germany.

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S LederbogenDepartment of Medicine, University of Essen, Germany.

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R HaaseDepartment of Medicine, University of Essen, Germany.

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B SallerDepartment of Medicine, University of Essen, Germany.

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C ReinersDepartment of Medicine, University of Essen, Germany.

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D ReinweinDepartment of Medicine, University of Essen, Germany.

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K MannDepartment of Medicine, University of Essen, Germany.

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Free access

OBJECTIVE: Several studies have suggested that iodine may influence thyroid hormone status, and perhaps antibody production, in patients with autoimmune thyroid disease. To date, studies have been carried out using large amounts of iodine. Therefore, we evaluated the effect of small 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 tested positive for anti-thyroid (TPO) antibodies or with a moderate to severe hypoechogenic pattern on ultrasound received 250 microg potassium iodide daily for 4 months (range 2-13 months). An additional 43 patients positive for TPO antibodies or with hypoechogenicity on ultrasound served as a control group. All patients were TBII negative. RESULTS: Seven patients in the iodine-treated group developed subclinical hypothyroidism and one patient became hypothyroid. Three of the seven who were subclinically hypothyroid became euthyroid again when iodine treatment was stopped. One patient developed hyperthyroidism with a concomitant increase in TBII titre to 17 U/l, but after iodine withdrawal this patient became euthyroid again. Only one patient in the control group developed subclinical hypothyroidism during the same time period. All nine patients who developed thyroid dysfunction had reduced echogenicity on ultrasound. Four of the eight patients who developed subclinical hypothyroidism had TSH concentrations greater than 3 mU/l. In 32 patients in the iodine-treated group and 42 in the control group, no significant changes in thyroid function, antibody titres or thyroid volume were observed. CONCLUSIONS: Small amounts of supplementary iodine (250 microg) cause slight but significant changes in thyroid hormone function in predisposed individuals.

 

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