Dietary iodine

Iodine. Of the 10—20 mg of iodine in the adult body, 70—80 wt % is in the thyroid gland (see Thyroid and antithyroid preparations). The essentiahty of iodine, present in all tissues, depends solely on utilisation by the thyroid gland to produce thyroxine [51-48-9] and related compounds. Well-known consequences of faulty thyroid function are hypothyroidism, hyperthyroidism, and goiter. Dietary iodine is obtained from eating seafoods and kelp and from using iodized salt. 

The amino acid tyrosine is the starting point in the synthesis of the catecholamines and of the thyroid hormones tetraiodothyronine (thyroxine T4) and triiodothyronine (T3) (Figure 42-2). T3 and T4 are unique in that they require the addition of iodine (as T) for bioactivity. Because dietary iodine is very scarce in many parts of the world, an intricate mechanism for accumulating and retaining T has evolved. 

Spear, P.A. and T.W. Moon. 1985. Low dietary iodine and thyroid anomalies in ring doves, Streptopelia risoria, exposed to 3,-4,3 4 -tetrachlorobiphenyl. Arch. Environ. Contam. Toxicol. 14 547-553. 

Goiter enlargement of the thyroid gland as a consequence of inadequate dietary iodine. 

Medicinal or dietary iodine interferes with all in vivo tests of radioiodine uptake, producing low uptakes that may not reflect a true decrease in hormone synthesis. 

The iodide salt is used as a source of dietary iodine in table salt and animal feed in cloud seeding as a coating in cathode ray tubes as a temperature indicator and as a catalyst in organic reactions. 

Worldwide, the most common thyroid disorder is hypothyroidism resulting from dietary iodine deficiency. In iodine-replete areas of the world, most thyroid disorders are the result of autoimmune disease. The symptoms manifested in hypothyroid and hyperthyroid states are largely independent of any underlying disorder of the thyroid gland itself they are a function of the degree of hormone deficiency or excess. 

A normal rate of thyroid hormone synthesis depends on an adequate dietary intake of iodine. Iodine is naturally present in water and soil, although some soils contain very low amounts. As a result, seafood is a more reliable source of iodine than crop plants. Approximately 1.6 billion people in more than 100 countries live in areas where natural sources of dietary iodine intake are marginal or insufficient. A minimum of 60 j.g of elemental iodine is required each day for thyroid hormone synthesis, and at least 100 j.g/day is required to eliminate thyroid follicular cell hyperplasia and thyroid enlargement (i.e., iodine deficiency goiter). 

T4, T3, MIT, and DIT are stored outside the cell in the follicular colloid in peptide linkage within the Tg molecules. In normal humans on an iodine-sufficient diet, Tg makes up approximately 30% of the mass of the thyroid gland and represents a 2- to 3-month supply of hormone. The total amount of iodine contained as T4, T3, MIT, and DIT within Tg varies with the dietary iodine intake. 

Juvenile or adult patients with primary hypothyroidism (as indicated by low serum free T4 and high serum TSH concentrations) are usually treated with thyroxine with the aim of relieving symptoms and reducing the serum TSH concentration into the normal reference range. If the primary hypothyroidism is the result of iodine deficiency, then gradually increasing dietary iodine supplementation may also be instituted in addition to the thyroxine replacement therapy. Iodine supplementation alone may lead to the development of acute hyperthyroidism. 

An adequate dietary intake of iodine is essential to prevent hypothyroidism. In many areas of the world, dietary iodine intake is insufficient and must be supplemented. There is another element in which a dietary intake may be insufficient that is also associated with thyroid hormone metabolism. This element is... 

Erythrosin (Gr spi/fif/ocr-red), tetraiodofluorescein, was synthesized first by Gnehm [220] and named by him. It has been used as a food coloring for many years and is the red dye of maraschino cherries, Tylenol capsules, and bright red luncheon meats. It is known as FD C Food Dyers and Colorists 3 and has received substantial attention from the FDA over the last 10 years since it causes bladder cancer when ingested in huge amounts by rats. It has recently been banned as a food dye in the United States, but is a source of dietary iodine for the Japanese [221], It is also used as a stain. 

Talbot, J. M., Fisher, K. D. and Carr, C. J. 1976. A Review of the Effects of Dietary Iodine on Certain Thyroid Disorders. Federation of American Societies for Experimental Biology, Life Sciences Research Office, Bethesda, Md. 

Two neonates who had been given intravenous amiodarone as fetuses at 26 and 29 weeks and whose mothers had also taken it orally developed hypothyroidism (83). The authors suggested that low dietary iodine intake by the mothers may have contributed, by enhancing the Wolff-Chaikoff effect. 

Patients with multinodular goiter and thyroid autonomy, especially if they are elderly and/or live in areas of dietary iodine deficiency... 

Prophylaxis is generally not necessary Patients at risk should be closely monitored by endocrinologists after iodinated contrast medium injection In selected high-risk patients prophylactic treatment may be given by an endocrinologist this is more relevant in areas of dietary iodine deficiency Intravenous cholangiographic contrast media should not be given to patients at risk... 

Alderman, G. Stranks, M.H. (1967) The iodine content of bulk herd milk in summer in relation to estimated dietary iodine intake of cows. Journal of Science in Food Agriculture, 8, 151-3. 

Thyroid disorders may be divided into over- and underproduction of the thyroid hormones. These may be caused by thyroid gland disorders or disorders of the pituitary gland (TSH production) or hypothalamus (thyrotropin-releasing hormone release). Thyroid hormone deficiency in infancy may cause mental retardation if it is not corrected immediately after birth. For this reason, many states require thyroid function tests in all newborns. In adults, thyroid deficiency may be caused by Hashimoto s thyroiditis, an immune disorder, or dietary iodine deficiency, in which case it is called simple goiter. The term "myxedema" has been used to refer to hypothyroidism of whatever cause. Myxedemas may... 

Goiter is the human pathology of hyperplasia of the thyroid gland induced by the deficiency of dietary iodine. The disease is localized in those regions where soils are low in iodine or where seafood is not consumed. Fortification of fable salt with sodium iodide, where applied, has practically eradicated this disease. Unfortunately, many regions of the world do not practice this public health policy. 

Thyroid hormone synthesis requires oxidation of dietary iodine, followed by iodination of tyrosine to mono- and diiodotyrosine coupling of iodotyrosines leads to formation of the active molecules, tetraiodo-tyrosine, (T or L-th3rroxine) and triiodotyrosine (Tj or L-thyronine). 

For some trace elements, continued suboptimal dietary intake— in the presence of physiological, nutritional, or other metabolic stress— may eventually have a detrimental effect. Then additional dietary supplementation may have a health restorative effect. Such effects are most clearly demonstrated in experimental animals. Examples include the effects of boron in the presence of vitamin D depletion, or the need for increased vanadium when there is either an experimentally induced deficient or excess supply of dietary iodine. ... 

Use Feed additive, in table salt as source of dietary iodine (up to 0.01%), catalyst, cloud seeding. 

Hotz CS, Fitzpatrick DW, Trick KD, et al. 1997. Dietary iodine and selenium interact to affect thyroid hormone metabolism of rats. J Nutr 127 1214-1218. 

Relatively few studies have examined environmental influences on the development of autoantibodies. A complex relation is seen between dietary iodine and prevalence of antithyroid antibodies, with increased prevalence reported in relation to iodine deficiency and to excess intake. This issue is discussed in greater detail in section 8.10 on iodine. 

Iodine is a mineral that is required for the proper function of the thyroid gland. The thyroid gland extracts iodine from nutrients and incorporates it into various hormones. The once-common condition of goiter, an enlargement of the thyroid gland, is an abnormality that results from an effort to compensate for low iodine intake. Goiter can be prevented if iodine is included in the diet. Seafood is one of the best sources of iodine. In areas where seafood is not available, dietary iodine is easily obtained in the form of iodized salt, found in most grocery stores. 

Antithyroid drugs have been used in many patients to control the hyperthyroidism of Graves disease until a remission occurs. Early investigators reported that 50% of patients so treated for 1 year remained well without further therapy for long periods, perhaps indefinitely. More recent reports have indicated that a much smaller percentage of patients sustain remissions after such treatment. Increased dietary iodine has been implicated in the latter, less favorable rates. 

Copper (I) iodide Copper iodide (Cul) Copper monoiodide Copper(1 ) iodide Copper(l) iodide Cuprous iodide EINECS 231-674-6 EPA Pesticide Chemical Code 108301 HSDB 271 Hydro-Giene Natural marshite. Used as a feed additive, in table salt as source of dietary iodine, catalyst, in cloud seeding. Solid mpa 588-606° bp= 1290° d = 5.63 insoluble in all solvents. Atomergic Chemetals Blythe, Williams Ltd. Cerac Greet R.W. Co. Mitsui Toatsu Nihon Kagaku Sangyo Sigma-Aldrich Fine Chem. 

Swanson EW (1972) Effect of dietary iodine on thyroxine secretion rats oflactating cows. J Dairy Sci 55 1763-1770. 

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