Iodine is a trace mineral the body needs to make thyroid hormones, which are essential for normal growth and development. In your body, about 70 to 80% of iodine is found in the thyroid gland in the neck. The rest is distributed throughout the body, particularly in the ovaries, muscles, and blood. If your body does not have enough iodine, you can develop hypothyroidism (low thyroid hormone levels). Symptoms include sluggishness or fatigue, weight gain, dry skin, and sensitivity to temperature changes. Deficiency happens more often in women than in men, and is more common in pregnant women and older children. In infants and children, hypothyroidism can affect physical and mental development. Premature infants are especially vulnerable to iodine deficiency due to the premature separation from the mom's iodine supply.

The classic sign of iodine deficiency is an enlarged thyroid gland. Some people with hypothyroidism develop an extremely large thyroid, known as goiter. Today, iodine deficiencies in the United States and other developed countries are rare because iodine is added to table salt. Crops in developed countries are generally grown in iodine rich soil, so there is more iodine in food. In developing countries, however, where soil is often low in iodine, more than 1 billion people may be at risk for iodine deficiencies.

Iodine is also used to clean wounds, and iodine tablets can be used to purify water.


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