Iodine deficiency s a lack of the trace element iodine, an essential nutrient in the diet. It results in goiter (endemic goiter) as well as cretinism due to untreated congenital hypothyroidism, which results in developmental delays and other health problems. Prevention includes adding small amounts of iodine to table salt, a product known as iodized salt. Seafood is also a well known source of iodine.