Adrenocortical Function in Preterm Infants

ABSTRACT

Adrenal hormones are essential for the timely differentiation and maturation of fetal organs and the regulation of intrauterine homeostasis. These hormones play complex roles during fetal life, and they are believed to provide the cellular communication that coordinates maternal-fetal interactions. Cortisol serves to modulate functional adaptations for extrauterine life in the perinatal period. Serum cortisol levels of preterm infants are similar to basal levels reported for healthy full-term neonates. However, a rise of cortisol production is absent during illness. Compared with a fetus of a similar gestational age, premature maturation of the hypothalamic-pituitary-adrenal (HPA) axis is suggested in preterm infants; however, the inappropriate cortisol value observed in severe illness is due to immaturity of 11beta-hydroxylase activity and an immature response of the brain to stress. Cardiovascular instability associated with adrenal insufficiency is more frequent than formerly reported, and replacing glucocorticoids in the treatment of refractory hypotension is effective without an increase in short term adverse consequences. However, the diagnostic criteria and optimal management have not yet been determined. Thus, further understanding of perinatal adrenal function will provide insight into the improved management of preterm infants.