LA FUNZIONE IPOFISO-TIROIDEA IN ETA PERINATALE

The hypophysis-thyroid function in perinatal age was studied by assaying TSH and thyroid hormones (T ₃, T ₄) in: the cord blood of 1792 newborns of four gestational age groups (27-32 weeks, 33-34, 35-36, 37-42); and the venous blood at the fifth day of life in 72 term newborns. TSH levels decrease and T ₄-T ₃ levels increase significantly from the 27th to 35-36 wk of gestational age. There is a further significant increase of T ₄ after 35-36 wk. There are no differences in cord blood hormone levels between small and large for date newborns. TSH level in cord blood depends on the type of delivery; it is higher in babies with fetal-neonatal distress, lower in those born by caesarean section, intermediate in newborns born physiologically. No differences were observed in TSH levels between breast fed newborns and those on cow's milk based formulas. The increase of thyroid hormone levels along with the gestational age parallels that of the lecithin/sphingomyelin ratio in the amniotic fluid. A significant correlation exists between this ratio and T ₄ levels after the gestational age of 35-36 wk. The hypothesis of a role of thyroid hormone in the treatment of the neonatal respiratory distress syndrome is discussed.