Thyroid Function of Preterm Twins Having Breastmilk from Their Mothers Consuming Seaweed Soup Might Be Variable between Siblings: A Case Series

Abstract

Thyroid dysfunction is common in preterm infants. Breastmilk-fed (BMF) preterm infants in Korea often develop hypothyroidism because of excessive maternal iodine ingestion. Recently in our neonatal intensive care unit, we encountered three pairs of BMF preterm twins showing discrepancies in thyroid function at 1 month of age. Their mothers consumed seaweed soup daily during that time. Within each BMF pair, the amount of breastmilk intake was almost similar. However, thyroid function differed within twins. Urinary iodine concentrations were different within twins and not correlated with thyroid dysfunction. The clinical characteristics within each pair were not significantly different. In conclusion, thyroid function would be different even between BMF premature twin siblings despite the same amount of iodine intake and the similar conditions that are currently known to affect thyroid function. Therefore, serial evaluation of thyroid function in BMF preterm infants would be crucial.