Neonatal thyrotoxicosis treated with exchange transfusion and Lugol's iodine.

An infant with neonatal thyrotoxicosis was born to a mother who had become euthyroid after subtotal thyroidectomy for Graves' disease. Exchange transfusion resulted in a 50% decrease of serum thyroxine levels and thyroid stimulating immunoglobulins. After 10 days mild thyrotoxic signs reappeared with high serum thyroxine levels, which were treated successfully with Lugol's iodine for 4 weeks. TSI was undetectable at 7 weeks of age. TSI was present in breast milk.