Limited response to CRH stimulation tests at 2 weeks of age in preterm infants born at less than 30 weeks of gestational age

SummaryBackground The high incidence of glucocorticoid-responsive complications in extremely preterm infants suggests the immaturity of their adrenal function; however, knowledge of the hypothalamus–pituitary–adrenal (HPA) axis in extremely preterm infants is limited. Methods To clarify the characteristics of the HPA axis in preterm very low birthweight (VLBW) infants, we performed CRH tests repeatedly: at about 2 weeks of age and at term (37–41 weeks of postmenstrual age) for 21 VLBW infants with a gestational age (GA) <30 weeks at birth. Results Basal cortisol values at 2 weeks of age were significantly higher than those at term in VLBW infants < 30 weeks of gestation at birth (304·1 ± 146·3 nmol/l vs 184·7 ± 108·2 nmol/l). Response to corticotropin-releasing hormone (CRH) stimulation tests at 2 weeks of age was significantly lower than at term (delta cortisol 148·3 ± 90·7 nmol/l vs 271·8 ± 167·0 nmol/l, delta ACTH 3·9 ± 3·2 pmol/l vs 12·3 ± 9·2 pmol/l, respectively). We found that earlier GA contributed to the higher basal cortisol values, and antenatal glucocorticoid (AG) contributed to the lower response of cortisol to CRH tests at 2 weeks of age. Conclusions VLBW infants showed a characteristic pattern in the HPA axis at 2 weeks of age: higher basal cortisol values and lower response to CRH tests. This study suggested that AG was related to the lower response to CRH tests, at least partly.