Importance of iodine

Iodine is an essential trace element which is required for the synthesis of thyroid hormones. Thyroid hormone is needed for normal growth and is particularly critical for neurodevelopment of fetus and infant.1 In children the neurological and psychological defects are noticed if there is iodine deficiency (ID) during pregnancy and infancy.2 Iodine is distributed in the earth’s environment in an uneven manner. Iodide salt is depleted in many regions due to earth erosion, flooding and other natural causes. For these reasons the iodide concentration is high in oceans. Slow and incomplete iodine cycling in many regions is leaving drinking water and soils in low iodine condition. In healthy adults,>90 % dietary iodine is absorbed.3 From the circulation iodine is cleared mainly by the thyroid gland and kidney. Renal clearance of iodine is fairly constant but the thyroid clearance depends on iodine intake. The areas where iodine is sufficient, the adult thyroid traps ~60 mg of iodine/day to compensate the losses and to maintain thyroid hormone synthesis. Healthy adult body contains 10 to 20 mg of iodine, of which 70 to 80 % is in the thyroid gland. Thyroid hormone is released into the circulation by the thyroid gland. Iodine is released after the degradation of thyroid hormone in the periphery, enters the plasma iodine pool and can be used up by the thyroid gland or excreted by the kidney. More than 90 % of ingested iodine is excreted in urine.3 Recommended iodine intak