LYCOS RETRIEVER 
Iodine: Thyroid Hormones
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Iodine is a critically important component of thyroid hormones. There are four iodine atoms per molecule of l-thyroxine, and three per molecule of l-triiodothyronine. The highest content of iodine in food is found in fish, with lesser amounts occurring in eggs, milk, and meat. Fruits and vegetables contain little iodine. Without iodine supplementation, people in most inland areas of the world, particularly mountainous regions, have iodine deficiency. This was the case in the United States before iodinization of salt.
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Iodine is a requisite substrate for the synthesis of the thyroid hormones, the minimum daily requirement being about 50 micrograms. An autoregulatory mechanism within the thyroid serves as the first line of defense against fluctuations in the supply of iodine and ... permits escape from the inhibition of hormone synthesis that a very large quantity of iodine induces (Wolff-Chaikoff effect and escape therefrom). Environmental iodine deficiency continues to be a significant public health problem worldwide, compounded in some geographic regions by the presence of other goitrogens in some staple foods. The pathologic consequences of severe iodine deficiency include endemic goiter, endemic cretinism, increased fetal and infant mortality, and an increased prevalence in the community of cognitive and neuromotor disabilities. The implementation of an iodization program prevents endemic cretinism and reduces the frequency of the other pathologic consequences of iodine deficiency. Iodine excess results principally from the use of iodine-containing medicinal preparations or radiographic contrast media.
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Iodine has been used in the temporary treatment of hyperthyroidism (Grave’s disease). Hyperthyroidism is a disorder in which the thyroid is overactive, resulting in increased protein metabolism, calcium imbalance, glucose intolerance, and overall increased metabolism. Serum cholesterol and triglyceride levels are depressed, and the patient may complain of perspiration and heat intolerance. Iodine supplementation increases storage of the thyroid hormone thyroxine, helping to prevent its release.
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Iodine 131 is one of the radionuclides involved in atmospheric testing of nuclear weapons, which began in 1945, with a US test, and ended in 1980 with a Chinese test. It is among the long-lived radionuclides that have produced and will continue to produce increased cancers risk for decades and centuries to come. Iodine 131 increases the risk ofcancer and possibly other diseases of the thyroid and those caused by thyroid hormonal deficiency.
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Iodine is an essential constituent of the thyroid hormones thyroxine [3,5,3′5′tetraiodothyronine (T4)] and 3,5,3′-triiodothyronine (T3). The major role of iodine in nutrition arises from the important part played by the thyroid hormones in the growth and development of humans and animals. Iodine nutritional status can be assessed by means of goiter surveys, the determination of urinary iodine excretion and the measurement of levels of thyroid hormones and of the pituitary thyroid-stimulating hormone (TSH).
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Iodine is essential for the formation of thyroid hormone and a deficiency will cause goiter and primary hypothyroidism. In countries where iodine is deficient in the soil, rates of hypothyroidism and goiter from iodine deficiency are very high. In developed countries... because iodine is added to salt, iodine deficiencies are rare. It's possible to get iodine deficient, but it takes work. You would have to eat non-iodized salt, stay away from processed foods, and not eat iodine rich foods like seafoods.
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Thyroid Hormones