Corticotrophin-releasing hormone stimulation tests for the infants with relative adrenal insufficiency

BackgroundVery low birthweight (VLBW) infants are considered to be vulnerable to relative adrenal insufficiency (RAI); however, diagnosis is difficult in some clinical settings. Considering this background, it is necessary to establish a diagnosis of RAI in preterm infants. ObjectiveIn this study, we attempted to clarify the difference in response to CRH stimulation tests for preterm infants with or without RAI. MethodsBetween June 2009 and December 2015, we performed CRH stimulation tests for preterm infants born at a gestational age of <30weeks at around 2weeks of age. Retrospectively, subjects were classified into two groups: infants with RAI (n=9) or without RAI (n=17) based on the clinical symptoms and responsiveness to hydrocortisone. ResultsWe found no difference in base or peak serum cortisol levels related to CRH stimulation tests between the two groups; however, delta cortisol levels and responsive ratio (peak-to-base ratio) were significantly reduced in infants with RAI. 140nmol/L for delta cortisol or 1.5 times for peak-to-base ratio may be cut-off levels in preterm infants. ConclusionThis study provides evidence that base cortisol levels of preterm infants with RAI were not different from those without RAI; however, CRH stimulation tests may be a useful tool for the diagnosis of RAI in preterm infants.