Background: The purpose of this prospective study was to examine the hypothalamic-pituitary-adrenal axis using the corticotropin-releasing hormone stimulation test in 24 preterm infants (mean gestational age 27.4 +/- 1.4 weeks, mean birth weight 997 +/- 166 g) with bronchopulmonary dysplasia after completion of dexamethasone treatment.
Methods: The CRH stimulation test was performed before and two days after the course of dexamethasone therapy in a dosage of 1 microgram/kg body weight. Blood samples were obtained before and 30 minutes after application of CRH. The blood values for cortisol and ACTH were measured by radioimmunoassay.
Results: The mean basal cortisol level was significantly reduced from 338 +/- 283 nmol/l before dexamethasone treatment to 153 +/- 102 nmol/l after dexamethasone therapy. The site of HPA suppression was located to the pituitary gland as the mean basal ACTH level dropped from 9.5 +/- 5.2 pmol/l to 5.6 +/- 2.0 pmol/l after the dexamethasone course. In 9 infants there was only an insufficient increase of cortisol level after application of CRH as a possible sign of a reduced adrenal response. The patients with HPA-suppression did not differ in clinical aspects from infants without suppression of the HPA.
Conclusion: The results demonstrate a significant suppression of the adrenal and pituitary gland in very low birth weight infants with bronchopulmonary dysplasia after dexamethasone treatment. Before stressful situations like surgery we therefore recommend an investigation of the HPA.