Objective: To study the effect of L-thyroxine supplementation on neurologic maturation in very preterm infants with transient hypothyroxinemia.
Design: Randomized, double-blind, placebo-controlled, L-thyroxine supplementation trial.
Setting: Level III neonatal intensive care unit.
Subjects: A total of 200 infants <30 weeks' gestational age.
Intervention: Subjects were randomly assigned to receive L-thyroxine (8 microg/kg birth weight per day) or a placebo during the first 6 weeks of life.
Methods: Median nerve somatosensory evoked potentials were recorded, measuring cortical N1 peak latency at 2 weeks of age, at term, and at 6 months (corrected) age.
Results: Cortical N1 peak latency was not decreased significantly in the L-thyroxine group compared with the placebo group throughout the study period.
Conclusion: L-Thyroxine supplementation during the first 6 weeks of life did not decrease cortical N1 peak latency in infants of <30 weeks' gestational age.