The regulation of blood glucose, water homeostasis, nitrogen balance and blood pressure depend on adrenocortical function. In neonates, adrenocortical function is different to function in older infants and adults. Cortisol secretion doesn't follow the known circadian rhythm and little is known about patterns of secretion after the second day of life except that there are significant daily variations in cortisol levels. Clinical decisions, specially those concerning the treatment of low blood pressure are sometimes based on single determinations of cortisol levels.The present study was designed to establish a) normal daily variations in cortisol levels determined in serial samples of saliva in neonates, and b) the impact of gestational age and severity of underlying disease on these levels. To date, 18 neonates were sampled every 3 hours for 24 hours on day 3 of life, after stimulation of saliva production with a drop of lemon. Patients were divided into 3 groups:A: Healthy term, BW: 2820g; B: healthy preterm, BW: 1420 g; C:sick preterm, BW, 1610 g. Ranges (R) and Medians (M) of cortisol, in mcg/dl, for maximum (MxL) and for minimum levels (MnL) were determined. Results are presented in the Table. These data show significant variability in cortisol levels in all patients, with no trend towards a fixed pattern. Furthermore, we found no significant differences in levels between term and preterm infants or between healthy and sick neonates. We conclude that normal levels of cortisol are widely variable. We suggest that all decisions regarding treatment of low cortisol contemplate this extreme variability. Serial determinations of saliva levels in sick neonates can help in establishing the need for therapeutic intervention.

Table 1
Full size table