Circadian Rhythm of Cortisol in Infants

Abstract

Little is known about the diurnal pattern of cortisol secretion in infants. In spite of this one has to use a special dose scheme for replacement therapy in the case of cortisol deficiency. To investigate spontaneous cortisol secrition in early childhood we studied 17 infants (5 prematures, 5 newborns, and 7 infants at the age of 4 wks. to 6 ms.). They were compared with 5 older children (4-11 yrs.) and 5 adults (23-34 yrs.). During a 24 hour period blood was drawn every 60 min. in the infants and every 10-30 min. in older children and adults. Cortisol was assayed by a CPB-technique. Episodic cortisol variations were found in all groups. The 24 hour plot for premature and newborn infants did not show any of the extreme peaks or circadian rhythms present in the plots of the older infants, children, and adults. The quantities in the latter groups ranged between 30.3 ug/dl in the early morning and 0.2 ug/dl at night. The data suggest a lack of circadian rhythm of plasma cortisol until the age of 6 to 10 weeks. There may be a synchronisation between plasma cortisol variations and regular asleep/awake rhythms, which appear at this age in infancy. This study was supported by Deutsche Forschungsgemeinschaft