Immature adrenocortical function in preterm infants may cause inadequate production of cortisol under stress, resulting in adrenal insufficiency of prematurity (AOP).

The objective of this study is to compare cortisol production in preterm infants with and without late-onset AOP.

Of 27 preterm infants born at less than 32 weeks gestation, cortisol production was analyzed in those who did (patients, group P) and did not (controls, group C) eventually develop late-onset AOP.

Blood samples were prospectively collected every two weeks after birth, and steroid hormone concentrations in the pathway to cortisol production were measured retrospectively.