The Effect Of Critical Illness On ACTH, Cortisol And Aldosterone In Preterm Infants

Objective:In the state of emergency and stress, it is still unknown for their immature adrenal gland function how to change in preterm infant. To investigated the effect of illness on preterm infant's hypothalamus-putituary-adrenal (HPA) axis and weather to use glucocorticoid (GC), we measured the serum concentration of cortisol, aldosterone and adrenocorticotropic hormone (ACTH).Methods:Ninety preterm infants transferred to our hospital within 72 hours after birth, excluding genetic metabolic diseases, and the application of GC during perinatal period. These preterm infants were divided into two groups:gestational age (GA)≥34weeks'preterm infants and GA<34weeks'preterm infants. We collected their clinical data and measure serum cortisol, aldosterone and ACTH by radio immunoassay method within 72 hours after birth, day 7 and day 14 after birth.Results:(1) The serum cortisol concentration on severe illness preterm infant was higher than that on mild illness preterm infant. Among the GA≥34weeks'preterm infants, the serum cortisol concentration on severe illness infants was significantly higher than on mild ill infants within 72 hours after birth (t=-2.263, P=0.029).Among the GA<34 weeks'preterm infants, the serum cortisol concentration on severe illness infants was significantly higher than on mild ill infants on the day 14 after birth (t=-2.913, P=0.006). (2) The serum cortisol concentration was significantly decreased on 7d and 14d after birth than that within 3d after birth in the GA≥34weeks'preterm infants (F=4.679, p=0.012);, the serum cortisol concentrations weren't similar among different time points in the GA<34 weeks'preterm infants. (3) The serum cortisol concentration in death preterm infants was significant higher than that in survivor on 14d after birth. (4) Oxygen index (PO2/FiO2) was negatively correlated with serum cortisol concentration (correlation coefficient=-0.466, P=0.001). Low serum cortisol concentrations was not associated with increased morbidity and mortality.The serum cortisol concentrations of preterm infants with mechanical ventilation therapy and upper gastrointestinal hemorrhage were significantly higher than those of infants without mechanical ventilation therapy or no gastrointestinal hemorrhage (P<0.05). When the serum cortisol concentration was above the 75th percentile (P75), the incidence of mechanical ventilation therapy,glucose metabolism disorder, gastrointestinal hemorrhage,Ⅲ-Ⅳgrade periventricular-intraventricular hemorrhage and brain leukomacia, chronic lung disease, and mortality rate were increased strikingly. (5) Serum aldosterone and ACTH concentration were not modified by a variety of perinatal factors, such as gestational age, illness severity, and complication. Conclusions:1,The preterm infant already has the ability to response stimuli by regulating cortisol secretion. The greater the gestational age is, the more mature this ability is.2,The serum cortisol concentration is correlated with the severity of the disease, complications and prognosis.3,Serum aldosterone and ACTH concentration are not correlated with the severity of the disease.