Should a patient take oral steroids before an ACTH and morning cortisol lab test?

Oral Steroids Should Be Held Before ACTH and Morning Cortisol Lab Tests

Patients should not take oral steroids before ACTH stimulation testing and morning cortisol lab tests as they will interfere with results and lead to inaccurate assessment of adrenal function. 1

Rationale for Holding Steroids

• Interference with test results: Exogenous steroids will suppress the hypothalamic-pituitary-adrenal (HPA) axis and interfere with cortisol measurement
• False readings: AM cortisol in a patient on corticosteroids is not diagnostic as therapeutic steroids can be detected in the cortisol assay 1
• Timing requirements: Hydrocortisone needs to be held for at least 24 hours and other steroids for longer before endogenous adrenal function can be accurately assessed 1

Specific Steroid Holding Times

• Hydrocortisone: Hold for at least 24 hours before testing
• Prednisone/prednisolone: Hold for at least 48-72 hours
• Dexamethasone: Hold for at least 48-72 hours (preferred if testing must be done while on steroids as it has minimal cross-reactivity with cortisol assays) 2

Impact on Test Interpretation

Taking steroids before testing can lead to:

• False normal results: Exogenous steroids may be detected as cortisol in the assay
• False low results: HPA axis suppression from chronic steroid use
• Inability to diagnose adrenal insufficiency: The American College of Clinical Oncology guidelines state that "laboratory confirmation of AI should not be attempted in patients given high-dose corticosteroids for other conditions until treatment is ready to be discontinued" 1

Special Considerations

• Patients on chronic steroids: May have secondary adrenal insufficiency due to HPA axis suppression
• Recent steroid use: The guidelines note that "in a patient with adrenal insufficiency, a recent history of treatment with corticosteroids, and no other central hormone deficiencies, the HPA axis should be tested for recovery after 3 months of maintenance therapy with hydrocortisone" 1
• Emergency situations: If adrenal insufficiency is strongly suspected and testing is urgently needed while on steroids, dexamethasone can be used temporarily as it has minimal cross-reactivity with cortisol assays 2

Proper Testing Protocol

For accurate ACTH stimulation testing:

1. Hold oral steroids for appropriate duration based on type
2. Collect baseline morning cortisol (ideally between 6-8 AM)
3. Administer ACTH (standard 250 μg or low-dose 1 μg)
4. Measure cortisol at 30 and 60 minutes post-administration 3

Risk of Adrenal Crisis

If a patient has been on long-term steroids and has adrenal suppression, abruptly stopping steroids for testing could precipitate adrenal crisis. In such cases:

• Consider consulting endocrinology before testing
• Use a carefully managed steroid taper before testing
• Ensure patient education on symptoms of adrenal insufficiency
• Have emergency protocols in place 4

Proper timing of steroid discontinuation before testing is essential for accurate diagnosis and appropriate management of patients with potential adrenal insufficiency.