Thyroid Autoimmunity in Endemic Goitre Caused by Excessive Iodine Intake*

Abstract

The pathophysiology of endemic goitre caused by excessive iodine intake is not well defined. By interacting with the immune system, iodine excess may trigger the development of autoimmune thyroid disease such as lymphocytic Hashimoto's thyroiditis (LT). In an attempt to examine this further, we compared the presence of thyroid autoantibodies in 29 goitrous children, from an iodine excess area, and in 26 healthy children, from an iodine sufficient area, of north central China. Serum was tested for antimicrosomal (MAb), anti-thyroglobulin (TgAb), second colloid antigen antibodies (CA2-Ab) and TSH binding inhibitory immunoglobulins (TBII). Affinity chromatographically purified IgG was tested for thyroid growth-stimulating activity (TGI) by two different methods: a sensitive cytochemical bioassay (CBA) using guinea-pig thyroid explants and a mitotic arrest assay (MAA) employing a continuous rat thyroid cell line (FRTL-5). We found no increased prevalence of LT in patients with endemic iodine goitre. The levels of MAb, TgAb and CA2-Ab did not differ significantly between the two groups of children. Further, TBII were not present in either group. Thyroid growth-stimulating immunoglobulins (TGI) were the major autoantibodies found in children with goitres caused by iodine excess. In the CBA, 12 of 20 (60%) goitrous children and 0 of 12 (0% P less than 0.05) healthy children were positive for TGI. Similar results were found in the MAA, and a good correlation between results of the CBA and MAA was found (P = 0.003). Maximal TGI activity in dose-response CBA showed a good relation with clinical goitre size (r = 0.63; P less than 0.05) indicating a possible pathophysiological role for these antibodies. We conclude that endemic iodine goitre is not associated with Hashimoto's lymphocytic thyroiditis. Nevertheless, autoimmune growth factors such as TGI may play a primary role in the pathogenesis of thyroid growth in this condition.

Thyroid consequences of the Chernobyl nuclear power station accident on the Turkish population

“…On the basis of autoimmune thyroid diseases, it is again hard to conclude that Chernobyl has had an important role in the development of the autoimmune thyroiditis found in our study. Mean anti-Tg levels were significantly higher in the study subjects ð63:25^378:60 vs 51:97^333:32 IU=mlÞ; but mean anti-TPO levels were significantly higher in the controls ð24:14^219:09 vs 48:82^568:50 IU=mlÞ: Anti-Tg autoantibodies may be the result of the high iodine intake in the study group (38,39), because excess iodine intake may cause autoimmune thyroid disease by interacting with the immune system (40). But it is difficult to explain the higher anti-TPO level in the control group.…”

Thyroid Cell Proliferation-lnhibiting Activity in Serum of Patients with Chronic Renal Failure on Hemodialysis.

“…Iodine is reported to exert an inhibitory action on the growth of thyroid cells at various sites in both the cAMP-dependent and cAMP-independent regulatory pathways [20]. Boyages et al investigated autoantibodies in patients with endemic goiter [22] and found that thyroid growth immunoglobulin G was the major autoantibody class in children with goiters caused by iodine excess. They concluded that such autoimmune growth factors may play a primary role in the pathogenesis of thyroid enlargement in the presence of iodine overload.…”

Use of iodine for water disinfection: iodine toxicity and maximum recommended dose.

“…Various investigators have reported an incidence of hypothyroidism of 2-10% among American patients taking amiodarone (33). The pathophysiologic mechanism by which amiodarone leads to iodine-induced goiter may include the inducement of antithyroid antibodies and direct effects of the medication rather than simple suppression by iodine (32,39,46 Human experimental studies provide the best dose-response data, but most are of limited duration (Table 2). In several recent studies, researchers administered approximately 30 mg iodine/day for 1-12 weeks to healthy volunteers.…”

“…The average incidence of hyperthyroidism was 1.7%, but ranged as high as 7% in Sweden. Any increase in iodine intake will cause some increase in the incidence of hyperthyroidism in a previously iodine-deficient population (31,32). Most cases result from underlying multinodular thyroid disease when autonomous nodules that are not suppressed by increased iodine uptake produce excessive thyroid hormone (31,32).…”