Iodine: a Catalyst for Transient Congenital Hypothyroidism

Abstract Introduction: Iodine plays a key role in thyroid hormone metabolism. Excess iodine is an unusual cause of hypothyroidism. We report an infant with iodine induced abnormal newborn screen for congenital hypothyroidism. Case report: A Korean infant female was found to have an abnormal newborn screen for congenital hypothyroidism (CH) at 2 weeks of age. Investigation revealed markedly elevated urinary iodine. The infant’s diet consisted of breast milk alone, and her mother admitted to a diet rich in seaweed soup. It was recommended that the mother discontinue use of seaweed soup. The infant was initially treated with thyroid hormone replacement. Following withdrawal of the thyroid hormone replacement, the child remained euthyroid and developmentally normal. Discussion: Seaweed: a dietary staple of certain cultures is rich in iodine and maternal consumption of products with high iodine content while breastfeeding has been associated with congenital hypothyroidism. In the present case, the infant’s initial New Born Screen (NBS) was normal. The second newborn screen showed an elevated TSH with normal free T4. Conclusion: Iodine excess should be considered as a cause of an abnormal newborn congenital hypothyroidism screen, especially in the Asian culture.