Growth hormone, somatomedin C, and nonsuppressible insulin-like activity levels compared in premature, small, average birth weight, and large infants.

We have investigated the relationship between growth hormone, somatomedin C, nonsuppressible insulin-like activity, weight, gestational age, and 1-minute Apgar score in newborn infants. The 153 infants were categorized as small for gestational age (n = 19), average for gestational age (n = 59), large for gestational age (n = 60), and premature (gestational age at birth, 36 weeks or less (n = 15). Our study showed that (1) growth hormone levels were elevated in premature infants and correlated with Apgar scores and birth weights; (2) somatomedin C and nonsuppressible insulin-like activity levels were significantly lower in premature than in term infants; and (3) the birth weight of all infants studied had a significant overall effect on both somatomedin C and nonsuppressible insulin-like activity levels, suggesting that these factors may be involved in fetal growth. However, because in small for gestational age infants somatomedin C and nonsuppressible insulin-like activity were similar to levels in average for gestational age infants, it is suggested that other factors may inhibit fetal growth.