CORTICOSTEROID-BINDING GLOBULIN, TOTAL SERUM CORTISOL, AND STRESS IN EXTREMELY LOW-BIRTH-WEIGHT INFANTS

Our objective was to determine ii low levels of corticosteroid binding globulin (CBG) might explain the low serum total cortisol levels foun d in some extremely low-birthweight (ELBW) infants. In a prospective s tudy, serum total cortisol and CBG were measured in single blood sampl es from 31 ELBW infants, with a gestational age less than 28 weeks, in the first 8 days of life. Severity of illness was assessed using the Score for Neonatal Acute Physiology Perinatal Extension (SNAP-PE). The mean serum total cortisol (mean +/- 1 SD) was 9.2 +/- 9.8 mcg/mL and the mean CBG level was 1.4 +/- 0.31 mg/dL. There was no significant co rrelation between serum total cortisol and CBG levels (r = -0.18), sev erity of illness as measured by the SNAP-PE (r = + 0.12), or birth wei ght (r = -0.12). Five of 31 infants, having a mean SNAP-PE score of 41 , had serum total cortisol levels less than or equal to 3.0 mcg/dL. Es timated mean serum free cortisol concentrations in these five infants (0.76 mcg/dL) were comparable to estimated free cortisol levels diagno stic of adrenal insufficiency in sick adult patients. Our findings ind icate that CBC levels are lower in ELBW infants than in term infants, but low CBG levels do not explain the low serum total cortisol levels found in some very sick infants. Low cortisol levels in small prematur e infants may be adequate to support growth if the infant is well, but may result in a syndrome of adrenal insufficiency in those with sever e illnesses.