ESPE Abstracts

Introduction: The ACTH stimulation test is utilized to assess cortisol reserve and when non-classical congenital adrenal hyperplasia is suspected. Limited and conflicting data exist on the impact of the time of the day on cortisol response.

Aim: To study the association between peak cortisol response to ACTH test and time of the day it was conducted and to study the clinical parameters affecting this response.

Methods: This retrospective, single center study included 554 children (183 males, 0-20 years) who completed ACTH test between January 2023 and December 2023. Clinical and laboratory data were reviewed and compared between subgroups.

Results: The cohort was divided based on the timing of the ACTH test: morning, 08:30-11:59 (n = 67, 12.1%); noon, 12:00-14:59 (n = 288, 52.0%); afternoon, 15:00-16:59 (n = 98, 17.7%); and evening, >17:00 (n = 101, 18.2%). Peak cortisol <500 nmol/l was found in 11.9%, 11.8%,12.2% and 6.9%, respectively (P = NS). There was a trend towards higher peak cortisol levels among those who completed the ACTH test in the morning hours (P = 0.08). However, the delta cortisol (peak minus basal cortisol levels) was significantly higher among those who performed the test in the evening (P = 0.001). No differences in gender distribution, tanner stage, age, weight-SDS or height-SDS were observed between patients who had peak cortisol ≥500 nmol/l compared to those with a lower response. Of sixty-one patients (11.01%) with stimulated cortisol levels<500, twenty-one patients underwent a second ACTH test. Among them, twelve still had sub-optimal cortisol levels on the second test (27.6-494), in 9 (75%) of whom the test was performed in the morning hours. Nine patients (42.85%) had a cortisol level ≥500 in the second test: five conducted the test in the morning, one at noon, and three in the evening hours. Compared to those with peak cortisol <500 on the second ACTH test, both peak cortisol and delta cortisol were significantly higher in this group (P <0.001 and P = 0.03, respectively). In a univariate analysis, peak cortisol levels exhibited significant associations with age (Spearman’s rho=-0.133, P = 0.02) and BMI SDS (Spearman’s rho=0.140, P = 0.001). but not with height SDS or weight SDS.

Conclusion: The response to the ACTH test is not affected by the time of the day it is administered. Our results highlight the need for further investigation to establish standardized protocols to ensure the reliability and consistency of ACTH stimulation test in diagnosing adrenal insufficiency.