ESPE Yearbook of Paediatric Endocrinology

J Clin Endocrinol Metab. 2020 Dec 1;105(12):dgaa635. doi: 10.1210/clinem/dgaa635. PMID: 32901267.

The authors performed a retrospective analysis of low dose synacthen tests performed in 49 neonates from January 1, 2009 to September 30, 2017 in a tertiary-care pediatric center. Of samples measured at 15, 30, and 60 minutes, the majority of neonates showed a peak cortisol level at 60 minutes.

ACTH stimulation testing is used to assess adrenal insufficiency. There are 2 types of ACTH stimulation tests, low dose and high dose. The low dose is used in cases of secondary adrenal insufficiency (typically involves giving 1 μg/kg of corticotropin) and the high dose is used in cases of primary adrenal insufficiency. In neonates there is uncertainty whether the 30-minute cortisol sample is the optimal time for a single measurement and it is unknown what is the value of additional cortisol measurements for the low dose synacthen test.

The current findings contrast to previous evidence (1) on the timings of the peak cortisol on the low dose versus standard dose ACTH stimulation tests. Of cortisol values at 30, 40, 60 and 120 minutes: on the low dose test 9/10 neonates had a peak cortisol at 30 or 40 minutes; on the standard-dose test most peaks occurred at 60 or 120 minutes. Another study (2) reported that 94.9% of neonates had peak cortisol levels at 40 minutes (when tested at 0, 20, 30, and 40 minutes), with a clear rise in cortisol values across the time points. However, no sampling was undertaken after 40 minutes leaving the possibility that cortisol values might continue to rise after 40 minutes.

Thus, it is suggested that cortisol should be measured at 30 and 60 minutes when undertaking the low dose synacthen test in neonates with the 60-minute sample probably being more important. The 15-minute cortisol measurement does not add any additional value.

Reference: 1. Karlsson R, Kallio J, Toppari J, Kero P. Timing of peak serum cortisol values in preterm infants in low-dose and the standard ACTH tests. Pediatr Res. 1999;45(3):367–369.2. Sari FN, Dizdar EA, Oguz SS, Andiran N, Erdeve O, Uras N, Memik R, Dilmen U. Baseline and stimulated cortisol levels in preterm infants: is there any clinical relevance? Horm Res Paediatr. 2012;77(1):12–18.