What blood test is used to assess adrenal function during steroid weaning?

Blood Tests for Assessing Adrenal Function During Steroid Weaning

Morning serum cortisol measurement combined with ACTH levels is the preferred blood test to assess adrenal function during steroid weaning. 1

Primary Diagnostic Tests

• Morning serum cortisol:

  • Gold standard initial test for adrenal function assessment
  • Should be drawn at approximately 8 AM 2, 1
  • Interpretation thresholds:
    • ≥300 nmol/L (≥10.8 μg/dL): Excludes adrenal insufficiency 3, 4
    • <110 nmol/L (<4 μg/dL): Suggests adrenal insufficiency 3
    • Between 110-300 nmol/L: Further testing required 3, 5

• ACTH level:

  • Should be measured simultaneously with morning cortisol
  • Helps distinguish between primary and secondary adrenal insufficiency 1
  • Interpretation:
    • High ACTH + Low cortisol = Primary adrenal insufficiency
    • Low/normal ACTH + Low cortisol = Secondary adrenal insufficiency (common in steroid weaning)

Confirmatory Testing

• ACTH stimulation test (Synacthen test):
  • Indicated when morning cortisol results are inconclusive
  • Gold standard for confirming adrenal insufficiency 1
  • Procedure:
    • Administer 250 μg synthetic ACTH intravenously
    • Measure cortisol at baseline, 30 and 60 minutes
    • Normal response: cortisol >18-20 μg/dL at either 30 or 60 minutes 1

Monitoring Protocol During Steroid Weaning

For patients undergoing steroid weaning, the European Society of Endocrinology and Endocrine Society recommend 1:

1. Baseline morning cortisol and ACTH before beginning weaning
2. Regular monitoring during weaning process:
   • Monthly for first 6 months
   • Every 3 months for next 6 months
   • Every 6 months for 1 year 2
3. Additional testing if symptoms of adrenal insufficiency develop

Clinical Pearls and Pitfalls

• Timing matters: Cortisol has a diurnal rhythm; samples must be collected in the morning (around 8 AM) for accurate interpretation 1

• Medication interference: Many medications can affect cortisol levels:

  • Estrogen-containing medications can increase total cortisol
  • Certain anticonvulsants can decrease cortisol levels
  • Always check for medication interactions

• Risk assessment: Patients who received high-dose or long-term steroids are at higher risk of adrenal suppression 6

• Symptoms to monitor: Fatigue, weakness, dizziness, nausea, weight loss, and hypotension may indicate adrenal insufficiency during weaning 1

• Electrolyte monitoring: Consider checking electrolytes (sodium, potassium) as hyponatremia and hyperkalemia can occur with adrenal insufficiency 1

• Stress dosing education: Patients undergoing steroid weaning should be educated about stress dosing during illness or surgery 1

By using morning serum cortisol and ACTH levels as the primary assessment tools, clinicians can effectively monitor adrenal function during steroid weaning and identify patients who require continued steroid replacement or slower weaning protocols.