Does transient hypothyroxinemia cause abnormal neurodevelopment in premature infants?

THOP is a relatively common condition whose long-term effects remain uncertain. The preponderance of evidence indicates that at the very least THOP is a marker of elevated risk of neurodevelopmental adversity, but whether this association is truly causal and whether thyroxine treatment in the neonatal period can prevent adverse outcome is as yet unknown. Since the number of infants born and surviving at very early gestations continues to increase, the importance of this condition will be magnified in the future. The major difficulty in establishing the causal role of THOP is the tangled time order of events in the early neonatal period. It is therefore unlikely that further observational studies will advance understanding. Energies should be focused on Assessing neurodevelopment objectively in survivors in each of the TRH trials. Developing a new multicenter trial of newborn supplementation with thyroid hormone that is carefully planned to have sufficient power to assess neurodevelopment in treated and untreated infants under a variety of baseline conditions.