Use
One of the most important uses of iodine is in the treatment of hypothyroidism, a conditionin which the thyroid gland is deficient in iodine. Iodine deficiency may lead to the formationof a goiter, wherein the gland that surrounds the windpipe in the neck becomes enlarged.There are other causes of goiter, including cancer of the thyroid gland. A deficiency of iodinecan also cause cretinism (infant hypothyroidism) in newborn babies, which can result inmental retardation unless the subject takes thyroid hormones for a lifetime. Green leafy foods,among other foods, contain iodine that when taken into the human body ends up in thethyroid gland. Some food grown in iodine-deficient soils do not contain adequate iodine forour diets. This is why iodine was added to table salt (about 0.01% potassium iodide) decadesago, specifically for people who live in regions with iodine-poor soils. The area around theGreat Lakes in the United States is one region with soil that is deficient in iodine. A healthydiet requires 90 to 150 micrograms of iodine each day that, in addition to being available iniodized salt, can be obtained from eating a balanced diet, including seafood.The isotope iodine-131 is an artificial radioisotope of iodine used as a tracer in biomedicalresearch and as a treatment for thyroid disease. I-131 has a half-life of about eight days, whichmeans it will be eliminated from the body in several weeks.In industry, iodine is used for dyes, antiseptics, germicides, X-ray contrast medium, foodand feed additives, pharmaceuticals, medical soaps, and photographic film emulsions and as alaboratory catalyst to either speed up or slow down chemical reactions.Iodine is also used as a test for starch. When placed on starch (a potato for example), iodineturns the starch a dark blue color. Silver iodide is used in the manufacture of photographicfilm and paper. It is also used to “seed” clouds because of its ability to form a large numberof crystals that act as nuclei upon which moisture in the clouds condenses, forming raindropsthat may result in rain.