THYROID-FUNCTION IN PRETERM NEWBORNS - IS T4 TREATMENT REQUIRED IN INFANTS LESS-THAN-27 WEEKS GESTATIONAL-AGE

Thyroid hormones are essential for brain maturation. Very preterm infa nts, who are at risk of neurodevelopmental disabilities also have low T4 and FT4 values in the first weeks after birth. This transient hypot hyroxinemia may in part be causal to the neurodevelopmental problems. We have carried out a randomised. double-blind, placebo-controlled tri al with T4 in 200 infants <30 weeks' gestation. In the study groups as a whole (n = 100 in the T4 group, n = 100 in the Placebo group), no c lear effect of T4 administration was found. In this study we examined whether gestational age influenced the effect of T4 administration. Th e T4- and placebo groups were subdivided into 4 groups according to ge stational age, FT4-values during the first weeks after birth were lowe st in the youngest gestational age group in the T4 as well as in the p lacebo group. In this group with infants <27 weeks' gestation mental d evelopmental outcome at 2 years of age was significantly better than i n the placebo group of the same gestational age. There was also a tren d towards a better psychomotor and neurological outcome, Beyond 27 wee ks' gestation, no clear affect of T4 could be found: on the contrary, a possible harmful effect an mental developmental outcome might be the result. In conclusion, T4 treatment possibly improves developmental o utcome in infants <27 weeks' gestation, but seems not necessary beyond this gestational age.