Maturation of adrenal function determined by urinary glucocorticoid steroid excretion rates in preterm infants of more than 30 weeks of gestational age.

BACKGROUND

Data on the adrenal stress response of preterm infants between 30 and 36 weeks are inconsistent.

OBJECTIVE

To test the hypothesis that there is a positive association between illness severity and cortisol production rates (CPR) in preterm infants >30 weeks.

PATIENTS AND METHODS

In a prospective longitudinal observational study, glucocorticoid metabolites were profiled by gas chromatography-mass spectrometry in 24-hour urinary samples. Excretion rates of glucocorticoid metabolites were summed to calculate CPR in 61 well (mean +/- SD: 33.6 +/- 1.7 weeks) and 20 ill (33.2 +/- 1.6 weeks) preterm infants. Illness severity was measured by the score for neonatal acute physiology (SNAP).

RESULTS

During the first week of life, SNAP were higher in the group of ill compared to well infants. Medians of CPR (microg/kg/d per mg creatinine) in ill (well) infants were: 1st day, 31 (28); 2nd day, 24 (28); 3rd day, 27 (26); 5th day, 28 (17); 2nd week, 20 (19); 3rd week, 17 (19); 4th week, 16 (16); and 2nd month, 17 (23). There was a significant association between the maximum of SNAP and the maximum of CPR (OR 3.7; 95% CI: 1.2-11.5; p = 0.02) in a logistic regression model which comprised gestational age, mode of delivery, gender and the administration of prenatal steroids as covariables.

CONCLUSION

There was a positive association between severity of illness and CPR in preterm infants >30 weeks, indicating a maturation of the adrenal stress response.