Thyroid Function in Respiratory Distress Syndrome (RDS) of the Newborn

Abstract

Preliminary evaluation of thyroid function, utilizing total serum thyroxine (T4) and triiodothyronine (T3) resin uptake, was assessed following delivery in three groups of babies and their respective mothers; 40 premature new-borns with respiratory distress syndrome (RDS), 39 prematures comparable by gestational age who failed to develop RDS, and 22 full-term normal babies. The group of premature newborn infants in whom RDS occurred, as compared to the other two groups, had significantly lower mean total serum thyroxine levels and "free thyroxine index" (T4 x %T3 uptake/100). When matched by gestational age, the differences were also significant. Two days following delivery, the total serum T4 in the surviving prematures with RDS as compared to prematures without RDS was also significantly lower. The mean values for total T4 and "free thyroxine index" in the respective mothers of the three groups were not significantly different. Since L-thyroxine has been shown to increase the production of lung surfactant, widely accepted as deficient in RDS newborn infants, an association between lung immaturity and fetal thyroid function is postulated.