Iodine deficiency is when there is not enough iodine in the body. Iodine is an essential trace element. The thyroid hormones thyroxine and triiodotyronine have iodine. In areas where marine food is not eaten, there is low iodine in the diet. This causes iodine deficiency which gives rise togoiter (so-called endemic goiter), as well as cretinism, which results in developmental delays and other health problems.The Lancet has said, "According to WHO, in 2007, nearly 2 billion individuals had insufficient iodine intake, a third being of school age. ... Thus iodine deficiency, as the single greatest preventable cause of mental retardation, is an important public-health problem." Iodine deficiency causes diseases of the oral and salivary glands.