Growth hormone and somatomedin behaviour in the newborn.

Human growth hormone (HGH) and somatomedin (Sm) concentrations have been studied in a group of newborns. Plasma HGH values were 41.17 +/- 24.26 (SD) ng/ml (14.00-90.00 ng/ml) and the Sm value was 0.59 +/- 0.43 (SD) U/ml (0.18-1.8 U/ml); the difference between these values and the ones observed in normal adults (2.45 +/- 2.53 (SD) ng/ml and 1.16 +/- 0.28 (SD) U/ml respectively) were statistically significant. While growth hormone values were higher than in normal adult controls, somatomedin was significantly decreased. It is possible that the dissociation between human growth hormone and somatomedin in newborn could reflect a reduced biosynthesis of the somatomedin-generating system and consequently a lack of a feed-back control on GH exerted by somatomedin.