Iodine deficiency

[Dave Paprocki]

Iodine deficiency, which is common worldwide, can lead to enlargement of the thyroid gland.
The thyroid gland contains most of the iodine in the body. Iodine in the thyroid gland is necessary for the formation of thyroid hormones. (See also Overview of Minerals.)
Iodine occurs in seawater. A small amount of iodine from seawater enters the atmosphere and, through rain, enters ground water and soil near the sea.
In many areas, including the United States, table salt is fortified with iodine (in its combination form iodide) to help make sure people consume enough.
Iodine deficiency is rare in areas where iodine is added to table salt. However, the deficiency is common worldwide. People living far from the sea and at higher altitudes are at particular risk of iodine deficiency because their environment, unlike that near the sea, contains little, if any, iodine.

[Tanya Shivari]

In the body, iodine (I) is involved primarily in the synthesis of 2 thyroid hormones, thyroxine (T4) and triiodothyronine (T3).
Iodine occurs in the environment and in the diet primarily as iodide. In adults, about 80% of the iodide absorbed is trapped by the thyroid gland. Most environmental iodine occurs in seawater as iodide; a small amount enters the atmosphere and, through rain, enters ground water and soil near the sea. Thus, people living far from the sea and at higher altitudes are at particular risk of iodine deficiency.
Fortifying table salt with iodide (typically 70 mcg/g) helps ensure adequate intake (150 mcg/day). Requirements are higher for pregnant (220 mcg/day) and lactating (290 mcg/day) women.
(See also Overview of Mineral Deficiency and Toxicity.)
Iodine deficiency is rare in areas where iodized salt is used but common worldwide. Iodine deficiency develops when iodide intake is lt; 20 mcg/day.