Endocrine Abstracts

Background: Adrenal insufficiency (AI) is a potentially life-threatening condition if not identified and treated promptly. While the short Synacthen test (SST) remains the gold standard for diagnosis, it is not always available. Early morning cortisol (EMC) measurement is widely used as a practical screening tool; however, cut-off values vary across centres.

Aim: To assess the diagnostic accuracy of EMC levels in predicting AI using SST as the reference standard and to evaluate whether SSTs can be avoided in clear-cut cases.

Methods: This retrospective audit was conducted at Oxford Children’s Hospital and reviewed 134 records of patients who had EMC measurement between 2017 and 2023. Patients aged > 6 months and < 17 years, who had an early morning cortisol measurement taken within 30 days prior to the SST were included into analysis. An adequate adrenal response was defined as a peak cortisol ≥430 nmol/l at 30 minutes post-Synacthen. Collected data included demographics, clinical presentation, history of steroid exposure, EMC levels, and SST outcomes. Receiver operating characteristic (ROC) curve analysis was performed to assess the predictive value of EMC.

Results: A total of 42 patients (mean age 9.5 ± 5 years) were included. Adrenal insufficiency was diagnosed in 5 patients (11.9%), while 37 had normal SST responses. Presenting symptoms included hypoglycaemia (12%), recurrent vomiting (10%), and fatigue or lethargy (38%). Long-term steroid exposure was identified in 7% of the cohort. The median early morning cortisol level was 159.0 nmol/l in patients diagnosed with AI and 196.0 nmol/l in those without. ROC analysis yielded an area under the curve (AUC) of 0.76, indicating fair discriminatory ability of EMC. A cortisol threshold of <100 nmol/l strongly suggested AI, while levels >450 nmol/l reliably excluded it. Intermediate values were inconclusive and required confirmatory SST.

Conclusion: Early morning cortisol measurement demonstrates acceptable predictive value for diagnosing adrenal insufficiency. Thresholds <100 nmol/l (confirming AI) and >450 nmol/l (ruling out AI) can provide practical clinical guidance. This audit supports the role of early morning cortisol as an effective screening tool, potentially reducing the need for SST in clear-cut cases.