Chronic iodine excess

Effects Of Chronic Iodine Excess In A Cohort Of Long-Term American Workers In West Africa. / ClinEndocrinol Metab, Vol.87, pp 5499 -5502, ISSN 1945-7197 Pennington, J.A.T., Schoen, S.A., Salmon, G.D., Young, B., Johnson, R.D. Marts, R.W. (1995). Composition of Core Foods of the U.S. Food Supply, 1982-1991. III. Copper, Manganese, Selenium, and Iodine. / Eood Comp Anal., Vol.8, No.2, pp 171-217, ISSN 1096-0481... 

Minelli R, Braverman LE, Valli MA, Schianchi C, Pedrazzoni M, Fiaccadori F, Salvi M, Magotti MG, Roti E. Recombinant interferon alpha (rIFN-alpha) does not potentiate the effect of iodine excess on the development of thyroid abnormalities in patients with HCV chronic active hepatitis. Clin Endocrinol (Oxf) 1999 50(1) 95-100. 

Regarding the young infants, the point I wanted to make is that we are proposing to bring iodine levels from the chronic moderate but definitely deficient state up to the minimal levels compatible with normal thyroid function. This is entirely different from going from iodine deficiency to iodine excess ... 

I would tend to agree with you. When we estimated the incidence of Hashimoto s thyroiditis in Worcester, a suburb of Boston, we found that about 25 % of women over the age of 60-65 years have thyroid autoantibodies. Therefore, you find already there the potential in a large fraction of the population for iodine-induced hypothyroidism. I would suggest that, at least in North America, excess iodine should probably be avoided in elderly patients. This has been clearly shown in a study on the chronic administration of iodine-rich expectorants in a population of nursing homes. If I remember correctly, the authors reported an incidence of 6-7 % of hypothyroidism induced by iodine excess. 

In older patients with goiter due to iodine deficiency there is a risk of provoking hyperthyroidism by increasing iodine intake (p. 247) During chronic maximal stimulation, thyroid follicles can become independent of TSH stimulation ( autonomic tissue"). If the iodine supply is increased, thyroid hormone production increases while TSH secretion decreases due to feedback inhibition. The activity of autonomic tissue, however, persists at a high level thyroxine is released in excess, resulting in iodine-induced hyperthyroidism. 

Among other potential predisposing factors, treatment with iodine for 2 months in 21 patients with chronic hepatitis C receiving interferon alfa did not increase the likelihood of thyroid abnormalities compared with eight patients who received iodine alone, but abnormal thyroid tests were more frequent compared with 27 patients who received interferon alfa alone (522). This suggests that excess iodine had no synergistic effects on the occurrence of thyroid dysfunction induced by interferon alfa. 

Impact of Chronic Excessive Iodine Supplementation on Wistar Rats at Normal Iodine Baseline... 

Impact of chronic excessive iodine supplementation on the structure and function of the thyroid tissue... 

Chronic excessive iodine supplementation increased the apoptosis of thyroid follicular epithelial cells... 

Chronic excessive iodine supplementation persistently inhibited uptake and organization of iodine, thus leading to impaired synthesis and release of thyroid hormones... 

Chronic excessive iodine supplementation decreased the ability of antioxidation... 

Chronic excessive iodine supplementation inhibited the activity of 5 -deiodinase in thyroid and peripheral tissues... 

Effects of Chronic Excessive iodine Suppiementation on Thyroid from Wistar Rats at Deficient iodine Baseiine... 

Chronic excessive iodine induced the onset of autoimmune thyroiditis in NOD.H-2 mice, and the degree of lymphocytes infiltration showed a positive correlation with the dosage and the duration of iodine supplementation... 

Chronic excessive iodine promoted the reactivity of anti-thyroglobulin antibody... 

Chronic excessive iodine supplementation could cause goiter or retention of colloid in the thyroid. 

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