Should a patient stop taking oral steroids, such as prednisone (corticosteroid), before undergoing Adrenocorticotropic Hormone (ACTH) lab testing?

Oral Steroids Must Be Discontinued Before ACTH Testing

Patients should discontinue oral steroids before ACTH stimulation testing as these medications will interfere with results and lead to inaccurate assessment of adrenal function. 1

Why Steroids Interfere with ACTH Testing

Exogenous steroids directly impact the hypothalamic-pituitary-adrenal (HPA) axis in several ways:

• They suppress endogenous cortisol production
• They cross-react with cortisol assays, giving falsely elevated results
• They suppress the normal ACTH response

The American College of Clinical Oncology guidelines explicitly state that "laboratory confirmation of adrenal insufficiency should not be attempted in patients given high-dose corticosteroids until treatment is ready to be discontinued." 2

Timing of Steroid Discontinuation

Different steroids require different washout periods:

• Hydrocortisone: Hold for at least 24 hours
• Other steroids (like prednisone): Hold for longer periods 1

This timing is critical because:

1. Short-acting steroids clear more quickly
2. Long-acting steroids (like dexamethasone) may require several days to clear
3. The duration of HPA axis suppression varies based on dose and duration of steroid therapy

Safety Considerations When Stopping Steroids

Abruptly stopping steroids in patients on long-term therapy carries risks:

• Patients on chronic steroids may have secondary adrenal insufficiency due to HPA axis suppression
• Stopping steroids without proper planning could precipitate adrenal crisis
• For patients on long-term steroids, consultation with endocrinology is recommended before testing 1

Recovery of HPA Axis Function

Research shows variable recovery patterns after steroid discontinuation:

• A study found that HPA function is typically normal 1 week after discontinuation of a short burst of prednisone 3
• However, patients on long-term steroids may require months for full recovery
• The HPA axis should be tested for recovery after 3 months of maintenance therapy with hydrocortisone in patients with adrenal insufficiency related to prior steroid use 2

Clinical Approach to ACTH Testing in Steroid Users

1. For patients on short-term steroids:

   • Discontinue steroids at least 24-48 hours before testing
   • Monitor for signs of adrenal insufficiency

2. For patients on long-term steroids:

   • Consult endocrinology before testing
   • Consider a carefully managed steroid taper
   • Ensure patient education on symptoms of adrenal insufficiency
   • Have emergency protocols in place 1

Common Pitfalls to Avoid

• Testing too soon after steroid discontinuation
• Failing to recognize that a normal response to ACTH stimulation does not always indicate complete recovery of the HPA axis
• Not accounting for the possibility that patients may need steroid coverage during stress for extended periods (up to 5 years) after discontinuing long-term therapy 4
• Assuming all steroids have the same washout period

The accuracy of ACTH testing is essential for proper diagnosis and management of adrenal insufficiency, making proper preparation critical for valid results.