Iodine Deficiency

Iodine deficiency early in life impairs cognition and growth, but iodine status is also a key determinant of thyroid disorders in adults. Severe chronic iodine deficiency increases risk for goiter and hypothyroidism. In contrast, compared to areas of adequate iodine intake, mild and moderate iodine deficiency in populations increases nodularity and thereby risk of hyperthyroidism, particularly in older adults. Increasing iodine intakes in populations leads to a small increase in the incidence of subclinical hypothyroidism. The link between iodine intake and thyroid autoimmunity is complex; prospective surveys have reported mild increases in the occurrence of thyroid autoimmunity with antibodies at a low titer after salt iodization. There is no strong evidence that ranges of dietary iodine intake are linked to thyroid cancer incidence; however, correction of iodine deficiency may shift subtypes toward less malignant forms. Thus, ensuring adequate, but not excessive, population iodine intake is an important component of preventive health care to reduce thyroid disorders.