SEX-BASED DIFFERENCES IN SERUM LEPTIN CONCENTRATIONS FROM UMBILICAL-CORD BLOOD AT DELIVERY

Sex-based differences in serum leptin concentrations have been reporte d in adolescence and adulthood, To discover when such differences were generated, serum leptin concentrations were measured in umbilical cor d blood from 46 healthy infants and in the mother's blood at delivery. Considering the respective body weights of the mothers and infants (6 8.5+/-1.3 kg and 3.3+/-0.0 kg), umbilical cord concentrations of lepti n were disproportionately high in the infants (9.4+/-1.2 mu g/l) compa red with those in the mothers (18.7+/-1.3 mu g/l). There was a wide Va riation in the infant leptin Values (1.2-56.8 mu g/l) that did not cor relate with height, weight, cephalic circumference, or any other growt h-related parameter. The most striking differences emerged when result s were analysed by sex: umbilical cord concentrations of leptin in the girls (12.9+/-2.5 mu g/l) were significantly (P<0.01) greater than th ose in the boys (6.8+/-0.9 mu g/l), although no differences in leptin concentrations were observed between the mothers who gave birth to a g irl (19.5+/-2.2 mu g/l) and those who gave birth to a boy (18.1+/-1.7 mu g/l). The sex-based differences were not attributable to any growth -related differences between the sexes, except heavier placental weigh ts in the girls (P<0.007) than in the boys. These differences in lepti n concentrations may reflect a sex-based difference in the regulation of leptin production by the fetal adipose tissue.