Serum Leptin and Somatotropin Components Correlate with Neonatal Birth Weight

Abstract

Objective: To determine whether cord sera leptin and components of the somatotropin axis – growth hormone (GH), total (t) and free (f) insulin-like growth factor (IGF), IGF-binding protein-3 (IGFBP-3), and insulin – correlate with birth weight. Design: Cross-sectional study of 22 newborns, 12 with normal birth weight (NBW) and 10 with low birth weight (LBW), in a population of healthy mothers with an apparent normal pregnancy. Methods: Paired mother–neonate blood samples were obtained at vaginal delivery in order to measure leptin and the somatotropin axis components. Results: In all cases maternal blood concentrations of leptin, t and fIGF-I, its carrier protein IGFBP-3, and insulin were higher than in the cord sera of the newborns, regardless of their birth weight. On the contrary, maternal GH levels were lower than in their neonates. LBW neonates had decreased levels of leptin, tIGF-I, and IGFBP-3 as compared with those levels in NBW offspring; however, GH concentrations were higher in LBW neonates. Birth weight showed a significant correlation with cord sera leptin, tIGF-I, IGFBP-3, and GH; nevertheless birth weight was neither interrelated with fIGF-I nor with insulin levels. Conclusion: These data demonstrate that birth weight is significantly correlated with both leptin and some components of the somatotropin axis; on the other hand, no correlation was observed between leptin concentrations and each one of the components of the somatotropin axis. It is suggested that fetal leptin and the somatotropin axis cooperate in intrauterine growth and birth weight.