The low dose synacthen test: experience in well preterm infants.

A pilot study to establish what constitutes a normal response to the low dose synacthen test (using 500 ng/1.73 m2 of ACTH) in well preterm infants was carried out on seven well preterm infants. Previous studies on preterm neonates (using a dose of ACTH of 36 microg/kg) suggest that a normal adrenal response is a peak serum cortisol level of > or =360 nmol/l(24). The minimum peak serum cortisol achieved by our cohort was 358 nmol/l with 6/7 infants achieving more than 360 nmol/l. 71% attained a serum cortisol increment from basal level of > or =200 nmol/l. This pilot study suggests that the criterion used to denote a normal adrenal response in preterm neonates using a dose of 36 microg/kg of ACTH (which is a peak serum cortisol of > or =360 nmol/l) can also be a applied when a physiological dose of ACTH (as used in the low dose synacthen test) is used.