Sexual Disparity of Copeptin in Healthy Newborn Infants

Background: Arginine vasopressin (AVP) regulates water balance and blood pressure and plays a role in social behavioral processes. Healthy adult men as compared with women have higher blood levels of AVP and its C-terminal precursor peptide, copeptin. Objective: The objective of the study was to investigate whether sexual disparity of copeptin is present at birth. Methods: In 241 prospectively enrolled healthy newborn infants, 131 boys and 110 girls, plasma copeptin concentrations were measured at birth and on day 3 of life. Results: Multivariable linear regression analysis revealed stressful delivery (regression coefficient beta = .569, P < 0.001), acidosis (beta = -.347, P < .001), and male gender (beta = .132, P < .01) as independent determinants of copeptin at birth. In infants born without stress, that is by primary cesarean section (n = 81), male gender was the sole variable associated with copeptin (beta = .286, P < .05), copeptin concentrations being higher in boys[median5.5 pmol/L (interquartile range4.4-10.2)] than in girls [4.8 pmol/L (interquartile range 3.6-5.8), P < .05]. At day 3 of life, copeptin was determined independently by postnatal physiological dehydration (beta = .485; P < .001) and birth weight (beta = .279; P < .01). Conclusion: Sexual disparity of copeptin is already present at birth, indicating increased activation of the AVP system in newborn boys as compared with girls.