Effect of l-thyroxine supplementation on infants with transient hypothyroxinemia of prematurity at 18 months of corrected age: randomized clinical trial.

Abstract

Our objective was to evaluate effects of levothyroxine (l-T4) supplementation against neurodevelopmental outcomes at 18 months of corrected age in very-low-birth-weight (VLBW) infants with hypothyroxinemia but without elevated thyroid-stimulating hormone (TSH) concentration. VLBW infants who had plasma TSH concentrations <10 μU/mL and free thyroxine (FT4) concentrations <0.8 ng/dL between 2 and 4 weeks of age were enrolled. They were randomly assigned to either the Treated (n=25) or Untreated group (n=45). The Treated group received l-T4 at a dose of 5 μg/kg/day. We compared growth and neurodevelopmental outcomes at 18 months of corrected age in the two groups. There were no significant differences in growth, the incidences of developmental delay, cerebral palsy, visual impairment, and hearing impairment in the two groups. In such infants, l-T4 supplementation at a dose of 5 μg/kg/day did not affect FT4 levels and showed no beneficial effect at 18 months of corrected age.