Baseline and stimulated cortisol levels in preterm infants: is there any clinical relevance?

To evaluate the association between the cortisol levels and clinical outcomes in preterm infants.

Baseline adrenocorticotropic hormone (ACTH) and cortisol levels and ACTH-stimulated cortisol concentrations after low-dose synthetic ACTH (Synacthen®, 1 μg/kg) were measured in preterm infants <37 weeks of gestational age between the 5th and 7th days of life. Associations between cortisol concentrations and clinical outcomes were examined. The prevalence and prognostic utility of relative adrenal insufficiency (AI) were assessed.

Ninety-eight preterm infants were enrolled. Median baseline cortisol and ACTH levels were 13.7 μg/dl (25th-75th percentile, 9.7-21.1 μg/dl) and 11.5 pg/ml (25th-75th percentile, 6.9-22.6 pg/ml), respectively. Median peak cortisol level after ACTH stimulation was 33.6 μg/dl (25th-75th percentile, 27.2-40.2 μg/dl). The prevalence of relative AI, defined as baseline cortisol <15 μg/dl or Δ-cortisol <9 μg/dl, was 65%. Cortisol levels at baseline and at all time points during the test and relative AI were not associated with mortality or any other clinical outcomes.

Neither baseline nor ACTH-stimulated cortisol levels were associated with clinical outcomes in preterm infants. A significant proportion of preterm infants hospitalized in the neonatal unit fulfilled the criteria for relative AI; however, relative AI did not affect outcome.