IODINE. Iodine is an essential dietary element necessary for normal development and function of all vertebrates. Its sole physiological function is as a constituent of the thyroid hormones, thyroxine and triiodothyronine. It is removed from the blood by the thyroid gland for storage in organic form where it is found as iodinated amino acids in peptide linkage in thyroglobulin, a highmolecular weight protein.

Iodine is widely but usually sparsely distributed in nature, so that in vast areas of the world the supply in customary diets is marginal or insufficient. It has been estimated that over two billion persons are at risk of disorders attributable to iodine deficiency. Among these disorders are goiter, impaired intellectual function, growth retardation, reduced fecundity, lowered work capacity, increased rates of fetal loss and infant mortality, deafness, and in extreme instances a well-defined but somewhat varied...