Neonatal leptin levels are strongly associated with female gender, birth length, IGF-I levels and formula feeding.

Summary Objective  To investigate predictors of circulating leptin in healthy full-term newborns and to explore the relationship with anthropometric variables, serum levels of adiponectin and the major components of the IGF system at birth. To explore whether leptin levels are regulated by breastfeeding vs. formula feeding. Design  Observational cross-sectional study. Patients  Three hundred and nineteen healthy full-term newborns delivered during 1999 in Athens, Greece. Measurements  Anthropometric measurements, formula feeding information and blood samples were obtained. Leptin and adiponectin determinations were performed using a radioimmunoassay (RIA). Results  Multivariate regression analyses showed that leptin levels were positively associated with female gender, newborn length, ponderal index and IGF-I levels, but not with adiponectin levels. Newborns who were fed exclusively with milk formulas had more than twice the leptin levels of those who were exclusively breastfed. Conclusions  Leptin levels are positively related to female gender and anthropometric characteristics of neonates but, contrary to studies in adults, are not correlated with adiponectin levels. We also found evidence that formula feeding imparts a considerable increase in leptin levels in newborns.