Analysis of Cortisol Thresholds Using Newer Assays for Adrenocorticotropic Hormone Testing

Adrenocorticotropic hormone stimulation testing is used to diagnose adrenal insufficiency. Synthetic adrenocorticotropic hormone (cosyntropin) is administered, and cortisol levels are checked at baseline, 30 minutes, and 60 minutes. A peak cortisol threshold of 18 μg/dL is considered passing. In 2019, many cortisol assays shifted to more sensitive methods, resulting in lower cortisol values, which suggest modification of passing thresholds. We reviewed pass/fail rates by time point/threshold in 186 consecutive patients for cosyntropin stimulation tests using new assays and found that interpreting the results with a suggested lower threshold of 14 μg/dL shows significantly higher pass rates and, likewise, suggests the 60-minute assay adds minimal benefit.