[Iodine therapy for iodine deficiency goiter and autoimmune thyroiditis. A prospective study]

There is epidemiological and clinical evidence that iodine may induce or promote the manifestation of autoimmune thyroiditis. For this reason it is important to know if substitution of alimentary iodine deficiency or iodine treatment of endemic goitre can cause formation of thyroid antibodies. On the other hand the practical importance of this phenomenon should be evaluated.

During a prospective study we examined 209 patients with endemic non-toxic goitre and 53 healthy people. For treatment were used 200 micrograms iodine/d (n = 119), 500 micrograms iodine/d (n = 27), 1.5 mg iodine/week (n = 41), 150 micrograms iodine/d plus 75 to 100 micrograms T4/d (n = 26), 100 micrograms iodine plus 100 micrograms T4/d (n = 24). The observation took 1 year with a 3-month interval for check ups including clinical examination, ultrasound, TSH, T3, fT4, TPO- and thyreoglobuline antibodies and urinary iodine.

After 12 months 7.5% of iodine treated persons had produced antibodies, most of them at low levels. In healthy people we found increased antibody-levels in 3.8%, in patients with goitre in 9.0%, in patients with nodular goitres in 11.1%. 500 micrograms iodine caused the most antibody reaction in 14.8%. People treated with 200 micrograms iodine/d showed positive antibody levels in 5%. T4 seems to reduce antibody-reactions. Pathological antibody-levels were not found in patients with combined iodine/T4- and single-T4 therapy. Among the 22 primary pathological antibody levels only 4 increased further (18.2%). Three of them belonged to the group of 5 persons treated with 500 micrograms iodine/d. Primary high antibody values were normalized in 5 patients (22.7%). Hypothyroid disturbances were not found. Ultrasound did not show any alterations, and the reduction of thyroid volumes in antibody-positive patients was not affected. Median urinary iodine excretion during the observation-interval was 5.2 to 7.2 micrograms/dl.

Possible antibody reactions have no clinical importance at all. Individual cases must be observed. Low iodine doses should be preferred. Combined iodine/T4 treatment seems to have an advantage regarding immunological thyroidal reactions.