Endocrine Abstracts

Background: SSTs are performed in neonates for various indications and are important in identifying babies at risk of adrenal insufficiency who may require exogenous corticosteroids.

Objectives: To identify common indications for measuring cortisol in neonates, to determine which babies proceeded to have a SST, and to identify challenges and variations in how SSTs were performed.

Methods: We retrospectively evaluated all 55 babies in our NICU who had a cortisol level measured between January 2021-December 2022. We identified which babies proceeded to have a SST and reviewed patient notes to identify the indication for SST and any challenges and variations in performing the test.

Results: The average age when cortisol was first measured was 14.5 days with an average corrected gestation of 34+4 (range 22+6 --< 42+5). Common indications for measuring cortisol were persistent hypoglycaemia (24/55), conjugated hyperbilirubinemia (8/55), cerebral/spinal abnormalities (8/55) and electrolyte abnormalities (5/55), with some having >1 indication. 20/55 proceeded to undergo a SST, with 19/20 cases documented as discussed with paediatric endocrine. There was significant variation in how SSTs were performed. Cortisol was measured either once or twice post synacthen and at varying time points anywhere between 20-115 minutes. It was not always clear whether this variation was secondary to endocrine advice or other factors. In 5/20 cases at least one sample was not processed due to insufficient volume. Cortisol response was higher at 60 minutes compared to 30 minutes but declined after 105 minutes.

Conclusion: SSTs are conducted in our unit for clear indications and generally discussed with paediatric endocrinology. However, there is significant variation as to when cortisol is measured post synacthen and a risk of insufficient sampling. Measuring cortisol at 60 minutes vs. 30 minutes is more likely to exclude adrenal insufficiency, and this has been observed in multiple previous studies. While a single measurement at 60 minutes would reduce pain and blood loss in neonates, it is important to consider the impact delays or insufficient sampling may have on results when relying on a single measurement and we therefore recommend measuring cortisol at 30 and 60 minutes post synacthen.