Growth Hormone Responses to Growth Hormone Releasing Factor in Neonates

Abstract

The response of growth hormone (GH) to synthetic human growth hormone releasing factor (hGRF) administered intravenously was examined in 32 neonates aged 3–28 days. GH peaked at 30 min after hGRF administration and the mean ± SEM level of GH at maximal response was 66.4 ± 6.2 ng/ml. In the comparison between the neonates less than 7 days old and those more than 8 days old, between the neonates less than 37 weeks and those more than 38 weeks in gestational age, between the neonates under 2,500 g and those over 2,501 g in birth body weight, and between males and females, no significant statistical differences were observed.

Plasma somatotropin and somatomedin C concentrations following GRF or TRH injections in newborn calves

“…However, Shimano et al (1985) observed no difference when comparing response to GRF in babies less than 7 days old to that in neonates older than 8 days. In our experimental conditions, the increase in plasma GH concentration following the same dose (50 pmoles.kg-!…”

Growth Hormone and Growth Factors during Perinatal Life

“…At term [4], pituitary GH secretion is still enhanced compared with childhood, but there is a rapid decline of serum concentrations within the first postnatal days. Regulation by somatostatin and GH-releasing factor [5]is intact in term newborns. As the infant matures, there is a decrease in GH pulse frequency, pulse amplitude and nadir GH levels [4], resulting in a decrease of mean serum GH concentrations postnatally.…”

Growth Hormone Regulation by Growth Hormone-Releasing Hormone in Infant Rhesus Monkeys

“…Rhe sus monkeys have also shown a greater GH response to GHRH in the immediate new born period, with a striking decrease in GH response after 48 h of age [27], Furthermore, using similar restraint and sampling meth ods to those used in the current study, we have previously shown that the serum GH response to exogenous GHRH administra tion decreased with advancing age from 1 to 28 days in a group of rhesus monkeys stud ied longitudinally [28]. There was no correla tion between GH and cortisol concentra tions and no consistent change in cortisol with age [28], GHRH administration to hu man neonates produced no difference in GH response in 3-to 7-day-old infants compared to infants aged 6-28 days in one study [29], but GHRH produced a greater response in infants at 3 days of age than at 30 days of age in another study [30]. Thus, early neonatal evidence suggests that the spontaneous de cline in GH concentration observed during the first few days of life may reflect a de crease in pituitary response to GHRH stimu lation.…”