Glucocorticoid Trajectories in Preterm Infants - Born Too Soon, Wired Differently.

Context Levels of glucocorticoid (GC) precursors are elevated in preterm infants, whereas clinical signs of GC deficiency are frequently observed in neonatal intensive care units (NICU). Objective To describe the maturation of the GC metabolic pathway in preterm infants during the first year of life. Design And Setting Spot urinary samples (n=154) were collected in the NICU and at follow-up visits. Participants Sixteen preterm infants (8 boys) born <30 weeks of gestational age. Data of full-term infants were available from the same laboratory. Main Outcome Measures Urinary levels of GC precursor metabolites and 13 GC metabolites were quantitated by GC-MS. Enzyme activities were calculated by product/substrate ratios. Mixed models were used for statistical analyses. Results The levels of GC precursors remained high in preterm infants until term equivalent age (TEA), after which they decreased (p<0.001). However, GC production, estimated by the sum of 13 GC metabolites (sumGC) did not change significantly over time in preterm infants and was higher in preterm than in full-term infants after one week of age (p=0.044̶̶-<0.001). The sumGC/THS ratio (representing CYP11B1 activity) increased in preterm infants after TEA (p<0.001) while the 16α-OH-DHEA/5-PT ratio (representing 17,20-lyase activity) decreased (p<0.001). The ratio of cortisone metabolites to cortisol metabolites was higher in preterm infants before TEA than thereafter (p<0.001). Conclusions Despite a high production rate of GC precursors in preterm infants, the total GC production remained relatively constant and was regulated at the level of CYP11B1. Persisting differences between preterm and full-term infants in GC precursor levels as well as in GC production were observed, indicating possible programming effects of preterm birth.