Iodine (Symbol= I, Greek ioeides "violet-like" in regards to the colour of its vapour.-A non-metallic element. Iodine is essential for human metabolism. It is essential for the production of thyroid hormones in the thyroid gland. The thyroid hormones are manufactured in the thyroid gland, a gland located in the neck (in front and on the side of the oesophagus. Recall that a gland is a group of cells dedicated to producing a hormone. A hormone is a substance produced in one area of the body, such as a gland, and which affects a target tissue somewhere else in the body. In this case, the gland in question is the thyroid gland. The thyroid gland produces hormones called thyroid hormones. These hormones have the function of regulating metabolic rates of cells. In other words, when larger amounts of thyroid hormones are released into the blood by the thyroid gland, the hormones travel via the blood from the neck area (where the thyroid is found) and circulate throughout the body. Thyroid hormones are taken up by cells as the hormone passes them. The cells react to these hormones by increasing their metabolic rate, or rate of chemical reactions. This causes heat to be generated and other effects. This is necessary for various situations. For example, Eskimos have very high levels of thyroid hormones. This helps them generate more body heat in the much colder climate they dwell in.

Iodine is required for thyroid hormones, because elemental iodine is added to each thyroid hormone molecule. Iodine also has antibacterial properties and can be used for disinfecting cuts and abrasions.

RDA of iodine

Although iodine is necessary in human metabolism, an accurate RDA has not been established. The reason, and probably the reason for lack of RDA's of other trace elements, etc., is that metabolism varies among individuals, as well as weight, and various other factors. Therefore, the RDA for one individual may not be sufficient for another. Various figures ranging from 100 to 500 micrograms have been proposed. To avoid confusion, keep in mind that seafood is the best source of iodine. Eating seafood gives more than any amount recommended. for example, haddock supplies several thousand micrograms of iodine per kilogram of fishmeat. Therefore, including seafood in the diet will ensure that you get more than enough iodine. Other meats and vegetables contain varying amounts of iodine, but this is unpredictable because of low amounts of iodine contained in soils. The amounts of trace elements such as iodine in vegetables follows the same analogy as iron. Different soils have different amounts. Several multivitamins include iodine as a component. Additionally, salt purchased in the supermarket is usually not only sodium chloride (NaCl) or common table salt, but also comes with added iodine. This helps to ensure that some iodine is provided in the diet. In certain parts of the world where iodine in the soil is insufficient, stationary residents who do not take supplementary iodine have a risk of iodine deficiency and thus, goitre development. The soils in the Andes, Swiss Alps, and Great Lakes region of the USA are example areas, and in the days preceeding iodized salt, many people developed goitres.

The reason a goitre develops with iodine deficiency is quite simple: Remember, iodine is required fot the formation of thyroid hormones. In the normal situation, thyroid hormones are produced and released into the blood to be distributed throughout the body to controm metabolism. The level of thyroid hormones is closely monitored and regulated in the body. The brain can detect when the needed amount of thyroid hormones has been produced. When the right amount has been produced hy the thyroid gland, the brain detects this, and stops the thyroid gland from producing excess thyroid hormone. The brain does this by the use of a gland also ! Remember, glands are a group of cells that make hormone, intended to affect a target tissue. Therefore, the pituitary gland in the brain acts as a gland and produces a hormone, which stimulates the thyroid gland. Thr hormone produced by the pituitary gland is called TSH (thyroid stimulating hormone). This hormone simpley simply stimulates the thyroid into manufacturing and releasing thyroid hormone. If the pituitary stops sending this chemical messenger (TSH) to the thyroid gland, then the thyroid gland stops producing thyroid hormone. So, when there is enough thyroid hormone in the blood, the brain stops the thyroid from producing and releasing any more, by simply stopping the chemical signal (TSH) from the pituitary. This is another one of the fantastic homeostatic control mechanisms in the body.

So, why does the thyroid gland grow when there's a lack of iodine? When thyroid hormone is made, two main components are necessary: Iodine and thyroglobulin. Thyroglobulin is a proteint manufactured by the cells of the thyroid gland. Iodine is supplied by the diet. IF iodine is NOT supplied in the diet, thyroglobulin is STILL produced, but it is not effective because iodine is lacking. Therefore, the brain senses this lack of effective thyroid hormone, and sends increased amounts of TSh to the thyroid gland in order to stimulate it to make thyroid hormone. The increase in TSH causes the thyroid gland to produce large amounts of thyroglobulin, which accumulate in the thyroid gland, causing it to swell, resulting in a goitre.

Deficiency and Toxicity of iodine

Lack of proper amounts of iodine in the diet result in what we call a "goitre" or a greatly enlarged thyroid gland. When the amount of iodine available to the thyroid gland falls low