Endocrine Abstracts

JOINT1862

Introduction: Tertiary adrenal insufficiency (AI) resulting from glucocorticoid-induced hypothalamic-pituitary-adrenal (HPA) axis suppression is the commonest cause of AI. The morning serum cortisol levels recommended by recent National Institute for Health and Care Excellence (NICE), UK guidelines (1) to predict adrenal insufficiency (AI) are not derived from studies in patients with AI due to glucocorticoids, as such studies using modern immunoassays are scarce. The aim of this study was to identify morning cortisol cut-off that predict the 30-minute post-Synacthen cortisol, to safely use in clinical practice in children and adults without requiring an SST.

Materials and methods: A retrospective cohort study of paediatric and adult patients on long-term glucocorticoids with suspected or confirmed tertiary AI undergoing a short synacthen test (SST). The main outcome of the study was morning serum cortisol cut-offs with 95% and 99% specificity and sensitivity determined via receiver operating characteristic (ROC) curve analysis. A pass for the SST was defined as a post-synacthen 30-minute cortisol of ≧430 nmol/l using immunoassays, Vitros 5600 (Ortho Clinical Diagnostics) in paediatric cohort, and Elecsys II (Roche) in the adult cohort.

Results: One hundred and seventy three and 443 SSTs were included in the paediatric and adult cohorts, respectively, of which 32% and 36% were normal. The ROC curve analysis demonstrated that basal morning cortisol performed well in both cohorts with area under curve (AUC) of 0.77 (95%CI 0.70,0.85) and 0.89 (95%CI 0.85,0.92), respectively. Morning serum cortisol cut offs to predict a normal SST in children and adults were 280 and 285 nmol/l at 95% sensitivity, and 316 and 349 nmol/l at 99% sensitivity, respectively. In a longitudinal safety analysis carried out in the adult cohort, using the 95% cut off, 54 of 57 patients with morning serum cortisol values ≧285 nmol/l were weaned from glucocorticoids within three months.

Conclusion: This study shows that morning serum cortisol performs well in predicting SST outcome in both children and adults on glucocorticoids, with two different immunoassays. A cut off of ≧285 nmol/l can be safely used to wean glucocorticoids without the need for synacthen testing.

Reference: 1. Adrenal insufficiency: identification and management [NG243] [article online], 2024. Available from https://www.nice.org.uk/guidance/NG243.