Serum concentrations of adrenal steroids and their precursors as a measure of maturity of adrenocortical function in very premature newborns.
Relative adrenocortical insufficiency is often seen in sick premature newborns. As the human fetal adrenal cortex does not express the 3β-hydroxysteroid dehydrogenase (3β-HSD) enzyme before about 23 weeks of gestation, we hypothesized that this enzymatic step may be rate limiting in cortisol synthesis in premature infants of less than 28 weeks postmenstrual age at birth. We measured cord, first day (D0) and median fourth day (D4) serum 17-OH-pregnenolone (17-OHPreg), 17-OH-progesterone (17-OHProg), 11-deoxycortisol, cortisol (F) and dehydroepiandrosterone sulphate concentrations and calculated the substrate/product ratios in 67 infants with gestational age 23.6-33.1 weeks. The mean 17-OHPreg/17-OHProg ratio as a marker of 3β-HSD activity did not differ between the gestational age groups (gestational age <28 vs. ≥28 weeks: 0.40 vs. 0.48, p = 0.52 for cord, 3.1 vs. 2.4, p = 0.25 for D0, and 1.6 vs. 1.9, p = 0.62 for D4). In addition, the 17-OHPreg/17-OHProg ratio did not differ between the infants in the lowest F tertile compared to those in the highest F tertile group, and the serum 17-OHPreg and 17-OHProg concentrations were parallel with the respective F concentrations. We did not find evidence of significant immaturity in adrenal 3β-HSD activity in preterm infants between 24 and 28 weeks of gestation.