Iodine: deficiency and therapeutic considerations.

Iodine deficiency is generally recognized as the most commonly preventable cause of mental retardation and the most common cause of endocrinopathy (goiter and primary hypothyroidism). Iodine deficiency becomes particularly critical in pregnancy due to the consequences for neurological damage during fetal development as well as during lactation. The safety of therapeutic doses of iodine above the established safe upper limit of 1 mg is evident in the lack of toxicity in the Japanese population that consumes 25 times the median intake of iodine consumption in the United States. Japan's population suffers no demonstrable increased incidence of autoimmune thyroiditis or hypothyroidism. Studies using 3.0- to 6.0-mg doses to effectively treat fibrocystic breast disease may reveal an important role for iodine in maintaining normal breast tissue architecture and function. Iodine may also have important antioxidant functions in breast tissue and other tissues that concentrate iodine via the sodium iodide symporter.