Serum thyroglobulin levels in preterm infants with and without the respiratory distress syndrome. I. Cord blood study.

Cord serum levels of thyroglobulin (Tg) and thyroid stimulating hormone (TSH) in 147 term and preterm infants were related to gestation age, birth weight, respiratory distress syndrome (RDS), and several perinatal factors by means of multiple linear regression analysis. None of the perinatal factors influenced Tg and TSH cord serum levels. However, in infants who developed RDS, Tg and TSH cord serum levels differed significantly from values in infants who did not develop this syndrome. In RDS infants, significantly higher Tg values were found. Tg cord serum levels increased with birth weight in the "average" RDS infant (i.e. infants with birth weights according to the 50th percentile of the growth chart for their gestation age), while these levels decreased in the "average" non-RDS infant. In RDS infants TSH cord serum levels increased with increasing birth weight, while these levels did not vary in non-RDS infants. Although Tg and TSH cord serum levels in RDS infants increased during gestation, no correlation between Tg and TSH cord serum levels could be demonstrated. There was no correlation between Tg and TSH cord serum levels in non-RDS infants. Since we found a clear correlation between Tg cord serum levels and gestation age, but no correlation between Tg and TSH cord serum levels, we suggest that other phenomena are responsible for the high Tg levels such as organ immaturity.