Somatomedin-C/insulin-like growth factor-1 in infants with congenital hypothyroidism during the first week of life.

Levels of somatomedin-C/insulin-like growth factor-1 (Sm-C/IGF-1) were determined in whole blood collected on filter paper from 41 newborns with congenital hypothyroidism and 183 full-term neonates with normal thyroid function. The mean Sm-C/IGF-1 value of the untreated hypothyroid infants (0.10 U/ml) was virtually identical with that of the normal controls (0.11 U/ml). We are unable to confirm earlier findings of others that Sm-C/IGF-1 concentrations are lower in hypothyroid newborns than in normal infants.