Role of iodine status and consequences of inadequate intake

Dietary iodine intake is required for thyroid hormone production. Dietary iodine requirements change across the life cycle. Because of increased thyroid hormone production, increased renal iodine losses, and fetal iodine requirements in pregnancy, dietary iodine requirements are higher in pregnancy than they are for non-pregnant adults. Requirements are also increased in lactation because of secretion of iodine into breast milk. There is currently no biomarker to assess iodine sufficiency of individual patients. Population-level iodine sufficiency can be assessed by median urinary iodine concentrations, population goiter rates, and blood thyroglobulin levels. Effects of iodine deficiency include increased risks for stillbirth, miscarriage, congenital anomalies, and increased perinatal and neonatal mortality, hypothyroidism, and goiter. Most importantly, adequate iodine is essential for neurodevelopment early in life. Severe iodine deficiency in pregnancy has been associated with an average 12-13-point decrease in offspring IQ. Although less well studied, mild to moderate iodine deficiency is likely associated with more subtle intellectual deficits. While excess iodine exposure is not a widespread public health problem, it may be associated with thyroid dysfunction and increased risk for thyroid autoimmunity.