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

BACKGROUND

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.