[Neonatal blood aldosterone]

Postnatal aldosterone levels have been studied in 13 newborns from birth to the end of the 3rd day of life. The examinations were performed in children in whom blood samples were collected frequently for the clinical reasons (mostly because of suspected serologic incompatibility). Aldosterone level was measured by radioimmunoassay in the mixed cord blood and then at 2, 6, 12, 48, 72 hours after birth. Aldosterone concentration in the cord blood was 0.35 ng/dl and rapidly increased to 0.79 ng/dl during the first two hours after birth. The same value was obtained at the 6th hour of life. The mean aldosterone concentrations were 0.85 ng/dl at the 12th hour, 0.89 ng/dl at the 24th and 48th and 0.85 at the 72nd hour of life. Postnatal variation of aldosterone levels differs from previously investigated variations of glucocorticoids levels.