Circulating glucocorticoid bioactivity and serum cortisol concentrations in premature infants: the influence of exogenous glucocorticoids and clinical factors

Abstract

Glucocorticoids are widely used before preterm delivery and in preterm infants may bear serious adverse effects. Better knowledge about the circulating glucocorticoid milieu after glucocorticoid treatment could improve treatment modalities. Therefore, we investigated the influence of exogenous glucocorticoids and clinical factors on serum cortisol (F) levels and circulating glucocorticoid bioactivity (GBA) in preterm infants. Eighty-nine infants (gestational age (GA) 23.6-33.1 weeks at birth) were enrolled in a prospective cohort study in two tertiary neonatal centres. Cord, day of birth (D0), fourth day (D4) and 36 weeks postmenstrual age serum F and GBA levels were measured. The cord GBA was 5.8-fold and D0 GBA 2.3-fold higher in the infants exposed to antenatal steroids within 12 h before birth when compared with those unexposed or exposed >7 days before birth (95% CI 3.8-8.6; P<0.0001, and 1.8-3.0; P<0.0001 respectively). In the infants treated with early postnatal dexamethasone, D4 GBA was 1.7-fold (1.3-2.2; P<0.0005) higher when compared with levels in the infants without this treatment. Clinical factors indicating perinatal distress, such as Apgar scores <7 and low GA, were associated with higher cord, D0 and D4 serum F levels. Both ante- and postnatally administered glucocorticoids increase circulating GBA not attributable to endogenous F. Perinatal distress and preceding glucocorticoid treatment need to be taken into account when circulating glucocorticoid milieu is evaluated in preterm infants. The GBA assay may prove to be a useful instrument in the development of new glucocorticoid treatment strategies.