From the Guidelines
Fasting is not explicitly required for an AM cortisol stimulation test according to the latest guidelines. When considering the diagnosis and management of critical illness-related corticosteroid insufficiency (CIRCI), the Society of Critical Care Medicine (SCCM) and European Society of Intensive Care Medicine (ESICM) 2017 guidelines suggest using the high-dose (250-μg) ACTH stimulation test for diagnosis 1. However, these guidelines do not specifically address fasting requirements for the test.
In clinical practice, it is generally recommended to fast from food and beverages (except water) for 8-12 hours before the test to establish an accurate baseline cortisol level. Morning medications should be held until after the blood sample is collected unless instructed otherwise by a healthcare provider. Additionally, substances like caffeine, alcohol, and smoking should be avoided for at least 24 hours before the test as they can affect cortisol levels.
The test typically measures the response of the adrenal glands to adrenocorticotropic hormone (ACTH), which stimulates cortisol production, helping in the diagnosis of conditions such as adrenal insufficiency or Cushing's syndrome. It is essential to follow specific instructions provided by a healthcare provider, as protocols may vary between facilities. The focus should be on minimizing stress and ensuring the patient is well-rested before the test, as stress can elevate cortisol levels and potentially affect results.
Key considerations for the test include:
- Avoiding substances that can interfere with cortisol levels
- Following healthcare provider instructions for medication and fasting
- Minimizing stress before the test
- Ensuring the patient is well-rested before the procedure.
From the FDA Drug Label
- 2 Diagnostic Inaccuracies Cortisol levels and subsequent diagnosis of adrenocortical insufficiency following cosyntropin for injection administration may be inaccurate if patients are on certain medications because of their effect on cortisol or cortisol binding globulin levels.
The question of fasting for an AM cortisol stim test is not directly addressed in the provided drug labels. However, the labels do discuss the potential for certain medications to affect cortisol levels and the importance of stopping these medications before testing to ensure accurate results.
- Glucocorticoids and spironolactone may falsely elevate cortisol levels and should be stopped on the day of testing.
- Estrogen-containing drugs may increase cortisol binding globulin levels, potentially leading to inaccurate plasma total cortisol levels, and should be stopped 4 to 6 weeks before testing. There is no mention of fasting as a requirement for the test. 2 2
From the Research
Fasting for AM Cortisol Stim Test
- The studies examined the use of cortisol stimulation tests to diagnose adrenal insufficiency, but did not specifically address fasting for an AM cortisol stim test 3, 4, 5, 6, 7.
- However, the studies did investigate the optimal timing and cutoff values for cortisol levels after cosyntropin stimulation, which may be relevant to the question of fasting for an AM cortisol stim test.
- For example, one study found that measuring cortisol levels at both 30 and 60 minutes after synthetic ACTH administration may be necessary to avoid overdiagnosing adrenal insufficiency 3.
- Another study established new diagnostic thresholds for cortisol levels using the Abbott Architect immunoassay, with a recommended cutoff of 14.6 μg/dL at 60 minutes after stimulation 4.
- A third study calculated new cortisol cutoff values for adrenocorticotropic hormone (ACTH) stimulation testing using newer specific cortisol assays, with recommended cutoffs ranging from 14 to 15 μg/dL depending on the assay used 5.
- A fourth study evaluated the performance of morning serum cortisol as a screening test for adrenal insufficiency, with a recommended cutoff value of 234.2 mmol/L 6.
- A fifth study compared total and free cortisol levels during different cosyntropin stimulation tests, with varying cutoff values for total cortisol and serum free cortisol 7.
Cortisol Stimulation Test Cutoff Values
- The studies suggest that the optimal cutoff values for cortisol levels after cosyntropin stimulation may vary depending on the assay used and the timing of the measurement 4, 5, 7.
- For example, one study recommended a cutoff of 14.6 μg/dL at 60 minutes after stimulation using the Abbott Architect immunoassay 4.
- Another study recommended cutoffs ranging from 14 to 15 μg/dL depending on the assay used 5.
- A third study found that a cortisol cutoff of 18 μg/dL during cosyntropin stimulation tests provided discrimination similar to insulin tolerance test, but only at 30 minutes during standard dose cosyntropin test 7.
Timing of Cortisol Measurement
- The studies suggest that measuring cortisol levels at both 30 and 60 minutes after synthetic ACTH administration may be necessary to avoid overdiagnosing adrenal insufficiency 3.
- One study found that 54% of patients reached peak cortisol levels at 60 minutes, and 11 patients who did not pass the test at 30 minutes did so at 60 minutes 3.
- Another study found that the best total cortisol cut-off during low dose cosyntropin test, medium dose cosyntropin test, 30 min and 60 min standard dose cosyntropin test were 14.6 μg/dL, 18.7 μg/dL, 16.1 μg/dL, and 19.5 μg/dL, respectively 7.