Iodine Supply

A recent study in Ireland supports the hypothesis that hmnan iodine intake in coastal regions depends significantly on the abundance of seaweed. [83] 

The technical exploitation of iodine may also be traced back to brown algae. Iodine was first discovered during the Napoleonic wars (1803-1815) in 1811 by the French chemist Bernard Courtois (1777-1838) in the course of isolating sodium carbonate from seaweed ash for the production of gunpowder. The addition of concentrated sulfuric acid to this ash not only resulted in serious corrosion of his copper vessels, but also led to the emission of a previously unobserved violet vapour. [83] 

21 Brown algae on the shore at Dunstaffnage, Scotland, at low tide. 

In the 19th century, iodine production fi-om seaweeds became a major economic activity in the coastal regions of Europe, in particular in parts of Brittany, Normandy, Ireland, and Scotland. 

iodine production is conducted in areas where brines from natural gas and oil fields contain high iodine concentrations. One of these sources is the brine from the Southern Kanto gas field in Japan, which contains approximately 100 ppm of iodine. 

---

If a euthyroid goiter has not persisted for too long, increasing iodine supply (potassium iodide tablets) can also be effective in reversing overgrowth of the gland. 

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. 

Diets rich in millet have been associated with endemic goiter in parts of West Africa where millet is a staple. The damage has been attributed to vitexin, a C-glycosyl flavone, that in rats has antithyroid activity and that in vitro inhibits thyroid peroxidase and the free radical iodination step in thyroid hormone biosynthesis. Isoflavones have produced similar antithyroid effects in rats, but clinical studies in adults have not. " However, this remains a possible concern in infants fed soya-based milk-replacers, especially if iodine supply is compromised. 

Mahillon I, Peers W, Bourdoux P, Ermans AM, Delange F. Effect of vaginal douching with povidone-iodine during early pregnancy on the iodine supply to mother and fetus. Biol Neonate 1989 56(4) 210-7. 

FI-1 FI-2 FI-3 H-1 S02 INPUT FLOW INDICATOR MAIN LOOP OUTPUT FLOW INDICATOR WATER SUPPLY INPUT FLOW INDICATOR H2S04 CRACKING FURNACE R 9 S-l TR-1 HYDROGEN PURIFICATION LOOP GAS-LIQUID SEPARATOR IODINE SUPPLY VESSEL OXYGEN PURIFICATION LOOP C02 -ACETONE TRAP... 

The thyroid gland is capable of adjusting its synthetic activity to the supply of iodine. When the iodine supply... 

Justus von Liebig (1842) introduced the fertilization of nitrogen and potassium in agriculture, and improved in this way the iodine supply of animals and man in Europe. This was effected in particular in Germany by the importation of Chile saltpeter, which contained up iodine at up to 1 g kg" ... 

The greatest contributors of iodine to humans of both sexes and eating a mixed diet are animal foodstuffs ( 75%), vegetable foodstuffs ( 15%) and beverages (10%) (Table 9-4.14). In 1996, eggs delivered 24% and dairy products 21% of the iodine intake (Anke et al. 2004). The iodination of industrially used salt, and its use by bakers, butchers and the preserves industry, may alter the percentage of iodine supplies. 

Tab. 9.4-25 Effect of iodine supply on total iodine content of the blood serum (I p,g L ) of goats, sheep and cattle...

Tab. 9.4-27 Effect of iodine supply on iodine content in biestings and mature milk of goats and cows ...

Tab. 9.4-28 Effect of iodine supply on the iodine content (jig kg DM) of white hair of goats and fattening bulls and white wool of sheep...

Anke M, Geoppel B, Muller M, Schulz E and Kramer K (1995b) The Iodine supply of humans depending on site, food offer and water supply. Z Anal Chem 352 97-101. 

Geoppel B, Anke M and Keonemann H (1985b) Influence of iodine supply on reproduction and the iodine content of milk, blood, hair and several other organs of ruminants. In Mills CF, Brenmer 1 and Chesters JK eds. Trace Elements in Man and Animals — TEMA 5, pp. 279 — 282. Commonwealth Agricultural Bureaux, Eamham Royal, Slough SL2 3BN, UK. 

Geoppel B, Kohler B, Scholz E, Anke M, Koebee R and Jaheeis G (1986c) In Anke M et al. eds. The effect of different iodine supply on the iodine content of blood serum, hair, milk and several oxtrathyroidal organs and tissues. 

The relative rates of synthetic activity at the various sites depend on the concentration of thyroid-stimulating hormone (TSH) and the availability of iodide, possibly accounting for the varying proportions of U and Tj depending on iodine supply. Limited iodine is utilized more efficiently in the synthesis of Tj, the transcriptionally active form, which contains three-fourths as much iodine as U. Eventually, iodine deficiency impairs synthesis of both and Tj and hypothyroidism results. In addition to the coupling reaction, intrathyroidal and secreted U is generated by the 5 -deiodination ofT,. 

It is known that iodide or iodate have a high bioavailability (>95%) in humans and animals. However, iodine in the diet may combine with different components and exist as organic iodine, which may have a low uptake in the digestive tract. During the last decade the iodine supply in many countries has increased significantly, but there is still a high frequency of goiter. This may be related to the iodine bioavailability in foodstuffs (Hurrell, 1997). 

It has been known that excessive iodine intake results in goiter, hypothyroidism, or hyperthyroidism in humans (Institute of Medicine, 2001). The biological basis for iodine-induced hyperthyroidism (IIH) appears most often to be mutational events in thyroid cells that lead to autonomy of function. When the mass of cells with such an event becomes sufficient, and the iodine supply is increased, the subject may become thyrotoxic. These changes may occur in localized foci within the gland or... 

Thus, 6-iodolactone seems to be generated within the thyroid cell membrane dependening on iodine supply, and inhibits not only cAMP-independent growth, but also induces apoptosis and seems to be involved in goiter involution induced by iodine. The same 6-iodolactone might also inhibit mammary breast cancer cells, and therefore seems not to be unique to the thyroid, but to all iodine trapping tissues. 

Growth of mammary breast cancer cells, which also express the same NIS as thyroid cells, is inhibited by iodine and also 6-iodolactone. Thus, a sufficient iodine supply has an important role, not only for thyroid function and growth, but also for the mammary gland. 2-IHDA, inhibits nicotinamide adenine dinucleotide hydride (NADH)-dependent H2O2 generation in vitro, as well as in vivo. It also inhibits adenylate-cyclase activity, and therefore is supposed to mediate the well-known Wolff—Chaikoff effect. 

All these direct effects on the thyroid supplement the indirect effects through the negative feedback of thyroid hormones in ensuring an inverse relationship between iodine supply and thyroid stimulation. 

The quantities drunk always have been limited by their sodium chloride content however, this formulation has been diminishing over the last few years. More diluted solutions, with the addition of carbonic acid, are being used increasingly nowadays, and the daily iodine supply varies from 13 mg in nondiluted waters down to 800 p,g in reduced iodine waters (Figure 36.1). 

Figure 36.1 Iodine supply by treatment with higher-mineralized iodine-containing waters. Iodine excretion at the beginning and at the end of a 21 days health resort treatment with administration of diluted Tassilo mineral spring water Tassilo light (left pair of columns) and a control group without prescription of iodine (right pair of columns). Iodine concentration in the morning urine was determined with the Sandell-Kolthoff method, modified by Wawschinek et ai, (1985) in the hospital of Barmherzigen Bruder. Permission of G. Thieme Verlag to use the illustration from previous source. Klieber and Winkler, (2006).

Table 36.2 Iodine supply by daily drinking of low- and high-mineralized iodine-containing mineral waters compared with the main iodine sources in our food...

The available data from in vivo, as well as from in vitro, experiments clearly demonstrate that soy isoflavones act as inhibitors of TPO and thus may influence iodine incorporation in thyroid hormone biosynthesis. On the other hand, most of the cfinical trials, including our own, have shown only modest and transitory effects of soy isoflavones on circulating thyroid hormone levels. However, they may be important in the case of insufficient iodine supply. Besides thyroid hormone biosynthesis, soy isoflavones may influence other events involved in thyroid function, such as iodine transport, thyroid hormone deiodination, and signaling pathways. So far, the data available on these topics is scarce and more experiments addressing these issues are needed. 

In conclusion, the clinical trials including ours have shown only modest and transitory effects of soy isoflavones on circulating thyroid hormone levels. However, they may be important in case of insufficient iodine supply. 

The fetus is totally dependent on maternal iodine supply throughout gestation, and on thyroxine supply during the first trimester of pregnancy for normal neurological development and nervous system maturation. It is therefore imperative that TH synthesis is adequate and is met with the appropriate iodine intake. Accordingly, it is important to know the trimester-specific reference intervals for THs and other thyroid functions in pregnancy. 

Previous studies demonstrated an improvement in the general iodine supply in different areas and different age groups in Europe. The underlying reasons for this improvement, and its consequences for thyroid pathologies, are not always obvious. 

Previous studies (as mentioned above) demonstrated an improvement in the general iodine supply in different areas and different age groups. The underlying reasons for this improvement (e.g., altered nutrition, use of iodinated salt) and its consequences for thyroid pathologies are not always obvious. To clearly assess a populations iodine status, the WHO recommended monitoring the iodine content in salt at the production level, measurement of urinary iodine concentration and carrying out surveys in large cohorts under local circumstances as the most suitable method for iodine status assessment (WHO, 2001). 

---