From the Guidelines
Measuring serum cortisol and Adrenocorticotropic Hormone (ACTH) levels at 9 am is a suitable approach when evaluating for adrenal insufficiency. This timing is considered optimal due to the natural circadian rhythm of cortisol secretion, which typically peaks in the morning 1. According to the guidelines, evaluating AM levels of ACTH and cortisol is a recommended step in the workup and evaluation of adrenal insufficiency 1.
Key Considerations
- The morning cortisol level can help diagnose adrenal insufficiency, with levels below 3 mg/dL suggesting the need for further evaluation 1.
- Measuring ACTH simultaneously with cortisol is crucial for distinguishing between primary and secondary/tertiary adrenal insufficiency 1.
- It is essential to collect samples before administering any glucocorticoids and to avoid acute stressors before testing to ensure accurate results.
Evaluation Process
- Evaluate AM levels of ACTH (if ≥ 23 ULN) and cortisol level (if ≤ 3 mg/dL) 1.
- Consider a standard dose ACTH stimulation test for indeterminate results (AM cortisol ≤ 3 mg/dL and ≤ 15 mg/dL) 1.
- Additional tests such as a basic metabolic panel, renin, and aldosterone levels, as well as an adrenal CT for metastasis or hemorrhage, may be necessary to complete the evaluation 1.
From the Research
Measuring Serum Cortisol and Adrenocorticotropic Hormone (ACTH) Levels
- Serum cortisol and ACTH levels can be measured at 9 am when evaluating for adrenal insufficiency, as evidenced by studies that investigated the diagnostic performance of basal cortisol levels at various times, including morning hours 2, 3, 4, 5.
- The studies suggest that morning serum cortisol levels can be used as a screening test for adrenal insufficiency, with proposed cut-off points ranging from 234.2 nmol/L to 354 nmol/L 2, 3, 4, 5.
- Measuring serum cortisol levels at 9 am can help identify patients with adrenal insufficiency, with a high degree of sensitivity and specificity, and can potentially reduce the need for ACTH stimulation tests in some cases 2, 4, 5.
- The relationship between morning serum cortisol and the short ACTH test has been studied, with findings indicating a strong correlation between the two, and suggesting that a mean basal morning serum cortisol level of ≥300 nmol/L can exclude the possibility of adrenal insufficiency 3.
- The use of morning serum cortisol as a screening test for adrenal insufficiency can facilitate diagnosis, as it is convenient and has a high diagnostic performance, and can potentially omit the need for short stimulation tests in almost half of the cases 4, 5.