Background: Ghrelin is secreted by the stomach, the hypothalamus, and the placenta in humans and has growth hormone-secreting and orexigenic properties. Leptin is secreted mainly by the adipocyte, plays a major role in energy balance, and reflects fat mass in infants as well as adults. Leptin and ghrelin central effects are mediated, at least partly, through the neuropeptide Y/Y1 receptor pathway in the hypothalamus.
Methods: We determined whether ghrelin is also present in the fetus and investigated its relationship to leptin, growth hormone, birth weight, and calf and abdominal circumferences in 90 full-term neonates.
Results: Immunoreactive ghrelin was detected in all cord samples (mean +/- SD, 187 +/- 88 pmol/L; range, 66-594 pmol/L). In contrast to leptin, ghrelin concentrations of boys and girls were not statistically different. In female neonates, ghrelin is inversely correlated with anthropometric measures. In male neonates, ghrelin is positively correlated with leptin and negatively with growth hormone.
Conclusion: The presence of significant ghrelin concentrations in all neonates before the first feeding is intriguing. Unlike the fairly constant concentrations and effects of leptin over the short term, the wide variability of ghrelin concentrations observed in newborns raises the possibility that ghrelin secretion causes short-term changes in feeding behavior. We suggest that ghrelin may play a physiologic role in the initiation of feeding.