Neonatal thyroxine supplementation in very preterm children:: Developmental outcome evaluated at early school age

Objective. Transient hypothyroxinemia in very premature infants is associated with developmental problems. A randomized, placebo-controlled trial of thyroxine (T-4) supplementation was conducted in a group of 200 infants <30 weeks' gestation. T-4 supplementation improved mental outcome at 2 years old in children of 25/26 weeks' gestation only. The effect of T-4 supplementation beyond 2 years of age is unknown. We present the effects of neonatal T-4 supplementation on outcome at early school age. Methods. Standardized measurements were used to assess cognitive, behavioral, and motor outcome, as well as a qualitative assessment of neurologic functioning. Survivors of the T-4 trial were assessed at the age of 5.7 years. Results. Ninety-nine percent of the 157 survivors participated. Outcome on all domains was comparable between the T-4 group and placebo group. In children <27 weeks' gestation, a 10 IQ point difference was found in favor of the T-4 group, whereas in children of 29 weeks' gestation, a difference of 15 IQ points was found in favor of the placebo group. Teachers' reports showed less behavioral problems in the T-4-treated children of 25/26 weeks' gestation, but more behavioral problems in the T-4-treated children of 27 weeks' gestation. Differences in motor outcome and neurologic outcome were in favor of the T-4-treated children <29 weeks' gestation, but not of the T-4-treated children of 29 weeks' gestation. Conclusions. We found benefits of T-4 supplementation for children <29 weeks' gestation, and especially in children of 25/26 weeks' gestation. However, in children of 29 weeks' gestation T-4 supplementation is associated with more developmental problems.