Maturational changes of urinary growth hormone excretion in the premature infant.

High plasma GH concentrations are observed in the newborn infant. To characterize the maturational change of GH secretion in premature infants, we serially measured 24-h urinary GH excretion in 30 premature infants. The gestational age ranged from 25-37 weeks and birth weight from 468-2415 g. Urinary GH excretion at 1 week of age was negatively correlated with gestational age, birth weight, and length of infants with adequate intrauterine growth. In the infants with 27 weeks of mean gestation (range, 25-28 weeks) mean urinary GH excretion was highest (6.1 micrograms/day) at the first week, decreased to 1.2 micrograms/day by the fourth week, and remained between 0.05 and 0.18 micrograms/day thereafter. When compared to the corresponding conceptional age, there was no postnatal difference in the pattern of GH excretion between infants with 27 and 31 (range, 29-32) weeks of mean gestational age. Persistent hyperexcretion of GH was observed in 4 of the 5 infants with intrauterine or postnatal growth retardation. Our results suggest that the postnatal change of 24-h urinary GH excretion is similar to ontogenic changes of plasma GH in fetus, and GH may have some effects on postnatal growth in premature infants.