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Thyroid Physiology   Thyroid Disease

Iodine Excess

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Katamine

Nutritional implications of high-iodine egg diet in rats: effects on lipid metabolism and thyroid function.

Katamine S, Tanaami S, Sekimoto K, Hoshino N, Totsuka K, Suzuki M.

Drugs Exp Clin Res. 1987;13(1):1-4.

[abstract only]

"The effects of a diet including high-iodine eggs, containing much higher amounts of iodine than ordinary eggs, were investigated on lipid metabolism and thyroid function in rats. To a non-purified diet was added at the 1% (w/w) level ordinary egg power (OE diet: 35 micrograms iodine/100 g diet) or high-iodine egg powder (IE diet: 392 micrograms iodine/100 g diet). At 7 months and 19 months, feeding of the IE diet resulted in a lowered serum tricylglycerol level, elevated tissue lipoprotein lipase activity and a lowered lipid peroxide level in the brain. Although the serum total iodine level was 5 times higher in animals given the IE diet than in those given the OE diet, serum levels of thyroid-related hormones (TSH, T3 and T4) were not affected by feeding of the IE diet. In animals exposed to cold and given antithyroid drug treatment, the IE diet seemed to improve age-related defects in thermogenic and thyroid hormone responses to cold, and also to confer resistance to the antithyroid drug. These results suggest that iodine ingestion through high-iodine eggs modulates both lipid metabolism and thyroid function in rats."

Iodine content of various meals currently consumed by urban Japanese.

Katamine S, Mamiya Y, Sekimoto K, Hoshino N, Totsuka K, Naruse U, Watabe A, Sugiyama R, Suzuki M.

J Nutr Sci Vitaminol (Tokyo). 1986 Oct;32(5):487-95.

[abstract only]

"Various meals being currently consumed by urban Japanese were determined for iodine. The meal samples were collected in 1982 and 1984. The habitual daily home meals of 4 middle-aged Japanese living in urban areas contained 45-1,921 micrograms (mean; 362, 361, 429 and 1,023 micrograms, respectively) of iodine per day. The regular meals served in two university hospitals contained 95-287 micrograms (mean; 195 micrograms) and 89-4,746 micrograms (mean; 1,290 micrograms) of iodine per day, respectively, and the diets for diabetes mellitus contained 59-144 micrograms (mean; 96 micrograms) of iodine per day. In the daily meals containing iodine exceeding ca. 300 micrograms, some kinds of seaweeds and, in some cases, several foods containing a red food color with low iodine bioavailability, erythrosine, provided a large portion of iodine. The iodine contents of refectory meals in a university were 47-203 micrograms (mean; 113 micrograms) per meal and those of lunches in two elementary schools were 25-31 micrograms (mean; 27 micrograms) and 18-43 micrograms (mean; 36 micrograms) per lunch, respectively. These results suggest that the current daily iodine intake of urban Japanese is not great and that erythrosine elevates the iodine content of meals."

Influences of feeding of high-iodine eggs on hypo- and hyperthyroid rats.

Katamine S, Tanaami S, Mamiya Y, Sekimoto K, Hoshino N, Totsuka K, Suzuki M.

J Nutr Sci Vitaminol (Tokyo). 1985 Oct;31(5):541-51.

[abstract only]

" The effects of the feeding of high-iodine eggs to rats with an abnormal thyroid status were investigated. Rats were fed for one week on a commercial diet supplemented with propylthiouracil (PTU) (10 mg/100 g diet) or thyroxine-Na (240 micrograms/100 g diet) respectively, to induce hypo- or hyperthyroidism, and then further fed for 4 weeks on the respective drug-supplemented diets, containing 1% (w/w) of either ordinary or high-iodine egg powder. Control (euthyroid) rats were maintained on the commercial diet. The induction of a hypothyroid state resulted in thyroid hyperplasia, with decreased thyroid iodine content, altered serum thyroid relating hormone levels (increased TSH and decreased T3 and T4), elevated serum total cholesterol and reduced serum triacylglycerol (TG) levels, and also increased muscle and adipose tissue lipoprotein lipase (LPL) activities. In contrast, in the hyperthyroid animals, thyroid atrophy, as well as decreased serum TSH and increased T3 and T4 levels, was associated with reduced serum total cholesterol level and muscle LPL activity. There were no essential differences between animals given high-iodine and ordinary eggs in either hypo- or hyperthyroid state, although the effects of PTU treatment on the thyroid and serum TG level appeared to be slightly lesser in rats given high-iodine eggs than in those given ordinary eggs. It is concluded that high-iodine eggs did not have any side-effect on either hypo- or hyperthyroid rat in this study."

Effects of the long-term (17-19 months) feeding of high-iodine eggs on lipid metabolism and thyroid function in rats.

Katamine S, Hoshino N, Totsuka K, Suzuki M.

J Nutr Sci Vitaminol (Tokyo). 1985 Jun;31(3):339-53.

[abstract only]

"The present paper describes the effects of long-term (17-19 months) feeding of high-iodine eggs on lipid metabolism and thyroid function of rats, and also the effects of inorganic iodine on lipid metabolism. Rats were meal-fed on a diet containing 1% (w/w) of ordinary egg powder (OE diet as control: 35 micrograms I/100 g) or high-iodine egg powder (IE diet: 392 micrograms I/100 g). After the 19-month dietary treatment, rats fed on the IE diet, compared with the controls, showed a higher tissue lipoprotein lipase activity, a lower lipid peroxide level in the brain and a trend toward lower serum triacylglycerol levels and body fat storage without alterations in serum levels of thyroid-related hormones (TSH, T3 and T4). From the results of cold exposure and anti-thyroid drug-treatment conducted on rats fed on the OE and IE diets for 17 months, high-iodine eggs seemed to improve the age-related defects in thermogenic and thyroid hormone responses to cold, and also to result in a resistance to the anti-thyroid drug. The effects of the IE diet on lipid metabolism of rats were partly exhibited by feeding of the OE diet with an equivalent amount of iodine added as KI or KIO3. Thus, it is suggested that iodine ingestion through high-iodine eggs modulates both lipid metabolism and thyroid function in rats."

Histopathological study on rats fed iodine-enriched eggs long-term (7 and 19 months).

Tanaami S, Katamine S, Hoshino N, Totsuka K, Suzuki M.

J Nutr Sci Vitaminol (Tokyo). 1985 Feb;31(1):29-42.

[abstract only]

"A histopathological study was conducted on rats fed on a diet containing iodine-enriched eggs over the long term, 7 and 19 months. A laboratory powder chow was added at the 1% (w/w) level with ordinary egg powder (ordinary egg diet as control: 35 micrograms iodine/100 g diet) or iodine-enriched egg powder (iodine-enriched egg diet: 392 micrograms iodine/100 g diet). The animals were meal-fed twice a day and allowed unrestricted voluntary wheel-running. In general, organs, tissues and endocrine glands including thyroid glands from rats of the iodine-enriched egg diet group exhibited no significant difference in histopathological features as compared with those of the ordinary egg diet group. These results suggest that long-term feeding of a considerable amount of iodine through an iodine-enriched egg diet did not cause any specific excess-iodine toxicity."

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