Iodine is a trace mineral that is important for the production of thyroid hormones. These hormones arenecessary for proper growth, nervous system development, and metabolism. Iodine deficiency only occurs if someone eats little or no bread, eats iodine or organic bread, and also does not use iodized table salt. With an iodine deficiency, the thyroid gland will slow down and swell (head). In children, iodine deficiency leads to growth retardation and reduced learning capacity and in the case of a large deficit to dwarfism.