Variations in cortisol response in patients with known and suspected adrenal insufficiency

Adrenal insufficiency (AI) is a relatively rare disease. While the adrenocorticotropic hormone (ACTH) stimulation test remains as one of the commonly used diagnostic test for AI, to date there is no consensus on the cortisol cutoff value post-ACTH stimulation test. This study aimed to investigate and characterize the cortisol response after the standard ACTH stimulation test in a group of Saudi Arabian patients. A single center retrospective study was conducted on Saudi Arabian adult patients who underwent ACTH stimulation test at the endocrinology clinics of King Abdulaziz Medical City in Riyadh, Saudi Arabia between 2015 and 2018. Demographic, clinical and biochemical variables were collected and analyzed. A total of 154 medical records of patients (44 males, 110 females, mean age 44.4 ± 17.0 years) were included in the study. All patients underwent ACTH stimulation test. Fatigue was the most common symptom of participants. Type 1 diabetes was the most frequent comorbidity. Cortisol levels were significantly lower in patients who received corticosteroid replacement therapy, and, within the context of ACTH stimulation tests, were useful in diagnosing AI in patients with vague symptoms and signs. For basal cortisol, the cutoff of ≤258.5 has a sensitivity and specificity of 69.2% and 58.6%, respectively. For 30-minute, the cutoff of ≤386 sensitivity and specificity are 61.5% and 69.0%. For 60-minute, the cutoff of ≤491.5 has a sensitivity and specificity of 61.5% and 65.5%, respectively. Higher cortisol cutoff values have better sensitivity. Patients with AI present with mostly nonspecific symptoms, with type 1 diabetes as the most common comorbidity. The cortisol level cutoffs obtained from Arab patients who underwent ACTH stimulation tests showed wide variability for its utility in AI diagnosis. Further studies to evaluate the optimal cortisol cutoff values for AI diagnosis in this population are needed.