Total and free cortisol plasma levels in pre- and postnatal life

Total and free cortisol and cortisol binding globulin (CBG) levels were measured in plasma of 7 fetuses during 22 to 34 weeks of pregnancy and 80 infants aged 1 day to 30 months. In comparison with normal adults, total cortisol levels were significantly diminished (p less than 0.001) both in fetuses and newborn infants aged 2 to 8 days. However, low total cortisol levels were accompanied by extremely low CBG concentrations especially in prenatal but also in early postnatal life. Consequently, free cortisol levels during pre- and postnatal life were not significantly different from those of normal adults except the values immediately after birth, which were evidently elevated. With advanced age of the infants CBG values increased and reached the mean values of adults at 46 to 80 days of age. However, in infants aged 8 to 30 months CBG values were even significantly higher (p less than 0.01) than those of adults.