Urinary free cortisol (UFC) values in newborns under stress

Children with adrenocortical insufficiency are commonly instructed to increase three to five times baseline glucocorticoid replacement dose during periods of stress such as surgery or febrile illness. The present study was undertaken to determine whether these recommendations reflect the actual change in urinary free cortisol (UFC) output during stress in neonates and to test the effect of stress on the diurnal variation of cortisol in this age group. Design and patients: Twenty-four hour urinary free cortisol (UFC) excretion was determined in 75 neonates during the first 2 days of life. Thirty were healthy and 45 were neonates with respiratory distress. In 60 babies the 24-h UFC was collected in 6-h fractions for the determination of diurnal variation of urinary cortisol. Results: The mean change in UFC was 4.5 times higher in the sick babies than in the controls. A distinct diurnal variation of UFC was noted in both healthy and sick babies. Conclusions: In contrast with previous publications a distinct diurnal pattern was noted in the majority of neonates.