II. Own investigation: Cortisol production rate in normal full‐term newborn infants and newborn infants of diabetic mothers as determined by the isotope dilution principle

Abstract

SummaryThe literature on the adrenocortical function in the early neonatal period is reviewed. The results of recent studies in this field are inconsistent with the assumption of a relative adrenocortical hypofunction in the neonate, formerly inferred from the earlier findings of low plasma levels of 17‐hydroxycorticosteroids and low urinary excretion of 17‐hydroxycorticosteroids in this period of life. It seems possible, however, that there is a relative depression of the adrenocortical function during the 12th to 36th hour of life as reflected by decreased plasma levels of 17‐hydroxycorticosteroids and diminished response to ACTH stimulation in this period; but, on the whole, the adrenal cortex in the newborn infant seems as active in relation to body surface area as in older age groups. The available data on the newborn infants of diabetic mothers hardly permit any conclusion as to their neonatal adrenocortical function in comparison with normal newborns.By means of an isotope dilution method cortisol production per 24 hours was studied between the 3rd and 6th day of life in 5 normal full‐term infants and 8 infants born to diabetic mothers. The validity of the method rests on certain assumptions which are discussed with special reference to its use in newborn infants. A comparison of the specific activities of different cortisol metabolites indicates not only that the method satisfies validity requirements, but that it has a reasonable degree of specificity and precision.The mean value for cortisol production per 24 hours in the normal infants was 4.7 mg, ranging from 3.5 to 6.1 mg. In the infants of diabetic mothers the mean value was 5.5 mg, ranging from 3.1 to 7.3 mg. There was no significant difference between these mean values. When corrected for body surface area the cortisol production per ma body surface ranged from 19.4 to 26.4 mgm2, with an average of 22 mg/m2 in normal infants, and from 13.8 to 37.8 mg/m2, with an average of 26.9 mg/m2, in the infants of diabetic mothers. There was no significant difference between the mean values. There was no obvious correlation between the cortisol production rates and the severity of maternal diabetes or the infants' appearance at birth. It seems probable that the new‐born infant produces more cortisol in relation to body surface area than the adult. When the production rates were expressed in terms of mg/m2 body surface area, there seemed to be a tendency towards higher values with decreasing gestational age. These findings are interpreted as a reflection of the increasing demands on the adrenal cortex during adaptation to extrauterine life.