What labs should be checked in a suspected adrenal crisis?

Laboratory Testing in Suspected Adrenal Crisis

When adrenal crisis is suspected, immediately draw blood for cortisol, ACTH, basic metabolic panel (sodium, potassium, CO2, glucose), and consider additional tests including creatinine, BUN, and calcium—but never delay treatment while waiting for results. 1, 2, 3

Essential Initial Laboratory Tests

Hormonal Assessment

• Morning serum cortisol and plasma ACTH are the first-line diagnostic tests and should be drawn before administering hydrocortisone if possible 1, 4
• Basal cortisol <250 nmol/L with elevated ACTH during acute illness is diagnostic of primary adrenal insufficiency 2, 3
• Basal cortisol <400 nmol/L with elevated ACTH during acute illness raises strong suspicion of primary adrenal insufficiency 2, 3
• Plasma renin activity (PRA) is increased in primary adrenal insufficiency 2
• Serum aldosterone and DHEAS levels are low 2

Electrolyte and Metabolic Panel

• Basic metabolic panel (sodium, potassium, CO2, glucose) should be obtained immediately 1, 4
• Hyponatremia is present in approximately 90% of newly presenting cases, though levels may be only marginally reduced 2, 3
• Hyperkalemia occurs in approximately 50% of patients—its absence does NOT rule out adrenal crisis 2, 3
• Hypoglycemia is common in children but less frequent in adults 2

Renal Function and Other Tests

• Increased creatinine and BUN due to prerenal renal failure from volume depletion 2
• Mild to moderate hypercalcemia occurs in 10-20% of patients at presentation 2, 5
• Metabolic acidosis may be present due to impaired renal function and aldosterone deficiency 2
• Elevated liver transaminases can occur in some patients 2
• Anemia, mild eosinophilia, and lymphocytosis may also be present 2

Critical Clinical Pitfalls

Common Diagnostic Errors

• Do not rely solely on electrolyte abnormalities—hyperkalemia is absent in 50% of cases and hyponatremia may be marginal 2, 4
• Paradoxical hypokalaemia and alkalosis can occur with severe vomiting instead of the expected hyperkalemia 2
• Treatment must NEVER be delayed for diagnostic procedures when adrenal crisis is clinically suspected 1, 3, 4

Timing and Treatment Sequence

• Secure blood samples for cortisol and ACTH prior to treatment if possible, but do not delay hydrocortisone administration 1, 3
• Administer IV hydrocortisone 100 mg bolus immediately followed by rapid IV 0.9% saline (1 L over first hour) 2, 6
• The diagnosis can always be established later, even after treatment has commenced 1, 7

Confirmatory Testing (When Diagnosis Uncertain)

Cosyntropin Stimulation Test

• Administer 0.25 mg cosyntropin (synacthen/tetracosactide) intramuscularly or intravenously 1, 4
• Measure serum cortisol at baseline, 30 minutes, and/or 60 minutes after administration 1, 4
• Peak cortisol >550 nmol/L (>500 nmol/L by some guidelines) is considered normal 1, 4
• This test is useful when initial results are indeterminate but should not delay emergency treatment 4, 7

Additional Etiologic Workup (After Stabilization)

Identifying the Cause

• 21-hydroxylase autoantibodies to identify autoimmune etiology in primary adrenal insufficiency 4
• Adrenal CT scan if autoantibodies are negative, to evaluate for metastasis, hemorrhage, or other structural causes 1, 4
• Evaluate for precipitating causes such as infection, which is the most common trigger 1, 6