Fetal iodine syndrome

Fetal iodine syndrome, also known as fetal iodine effects or iodine-induced neonatal hypothyroidism, is a condition that occurs when a fetus is exposed to excessive amounts of iodine during pregnancy. This excess iodine exposure — typically from maternal use of iodine-containing medications (such as amiodarone or iodine-based antiseptics), contrast agents, or excessive dietary iodine supplementation — can disrupt normal thyroid gland development and function in the fetus. The condition primarily affects the endocrine system, specifically the thyroid gland, through the Wolff-Chaikoff effect, in which high iodine concentrations inhibit thyroid hormone synthesis. Affected newborns may present with congenital goiter (enlarged thyroid gland), neonatal hypothyroidism, and in some cases respiratory distress due to tracheal compression from the goiter. Clinical features can include lethargy, poor feeding, prolonged jaundice, constipation, hypotonia, and signs consistent with thyroid hormone deficiency. If untreated, neonatal hypothyroidism can lead to impaired neurodevelopmental outcomes. The condition is classified under ICD-10 code P72.2 (other neonatal hypothyroidism, including transient neonatal hypothyroidism due to iodine exposure). Management involves prompt identification and withdrawal of the iodine source, along with thyroid hormone replacement therapy (levothyroxine) when hypothyroidism is confirmed. In many cases, the hypothyroidism is transient and resolves once the excess iodine is cleared from the infant's system, though careful monitoring of thyroid function is essential. Severe goiter causing airway compromise may require urgent intervention. Prevention through careful management of maternal iodine exposure during pregnancy is the most effective strategy.

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