What are the clinical manifestations of adrenal insufficiency and which laboratory tests should be ordered to evaluate it?

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Adrenal Insufficiency: Clinical Manifestations and Laboratory Evaluation

Suspect adrenal insufficiency in any patient presenting with unexplained fatigue, weight loss, hypotension, hyponatremia, or hyperkalemia, and immediately order morning cortisol and ACTH levels, followed by a short corticotropin stimulation test (250 μg) if initial results are equivocal. 1

Clinical Symptoms to Recognize

The symptoms of adrenal insufficiency are notoriously nonspecific and often lead to delayed diagnosis, which directly worsens long-term quality of life 1. Watch for:

Chronic Symptoms (Primary Adrenal Insufficiency)

  • Fatigue and weakness (most common, present in nearly all patients)
  • Weight loss and anorexia
  • Postural dizziness (from orthostatic hypotension)
  • Abdominal discomfort
  • Hyperpigmentation - This is specific to primary adrenal insufficiency only, appearing on sun-exposed areas, skin creases, mucosal membranes, scars, and breast areola 1
  • Salt craving (from mineralocorticoid deficiency)

Acute Crisis Symptoms (Medical Emergency)

  • Severe weakness and syncope
  • Abdominal pain, nausea, vomiting (may mimic acute abdomen)
  • Back pain
  • Confusion or reduced consciousness
  • Hypotension refractory to fluids 1, 2

Critical pitfall: In children, hypoglycemia and seizures are more prominent features than in adults 1, 2. In the presence of severe vomiting, you may paradoxically see hypokalemia and alkalosis rather than hyperkalemia 2.

Physical Examination Findings

  • Hyperpigmentation (primary AI only - compare to siblings' baseline pigmentation)
  • Low blood pressure with increased postural drop
  • Failure to thrive (in children)
  • Abdominal tenderness/guarding (in crisis) 1

Laboratory Tests to Order

Initial Screening Tests

Routine laboratory abnormalities that should trigger suspicion 1, 2:

  • Hyponatremia (most common, present in majority at diagnosis)
  • Hyperkalemia (present in approximately 50% at diagnosis)
  • Hypoglycemia (especially in children, rare in adults)
  • Hypercalcemia (10-20% of patients, mild to moderate)
  • Anemia, mild eosinophilia, lymphocytosis
  • Elevated liver transaminases

Confirmatory Hormonal Tests

The diagnostic algorithm 1, 2:

  1. Morning (8 AM) plasma cortisol and ACTH - First-line screening

    • Cortisol <100 nmol/L (<3.6 μg/dL) with elevated ACTH suggests primary AI
    • Cortisol <250 nmol/L (<9 μg/dL) with elevated ACTH in acute illness is diagnostic of primary AI 2
    • Cortisol <400 nmol/L (<14.5 μg/dL) with elevated ACTH in acute illness raises strong suspicion 2

  2. Short corticotropin (Synacthen) stimulation test (250 μg) - Gold standard for confirmation 1

    • Peak cortisol <500 nmol/L (<18 μg/dL) at 30 or 60 minutes is diagnostic of primary AI 2
    • This test should be performed when patient's condition allows

  3. Plasma renin activity (PRA) - Elevated in primary AI (distinguishes from secondary AI)

  4. Aldosterone level - Low in primary AI

  5. DHEA-sulfate (DHEAS) - Low in primary AI 2

Important caveat: In secondary adrenal insufficiency, cortisol is low but ACTH is normal or low (not elevated). The short corticotropin test may give false-normal results in secondary AI, requiring insulin tolerance test or metyrapone test for definitive diagnosis 3.

Additional Tests for Etiology

Once AI is confirmed, determine the cause 1, 2:

  • 21-hydroxylase (anti-adrenal) autoantibodies - First test for etiology (positive in autoimmune AI, the most common cause in Western countries)
  • CT imaging of adrenals - If antibodies negative, look for infiltration, hemorrhage, tuberculosis, or metastases
  • Very long-chain fatty acids - In males with negative antibodies, to exclude adrenoleukodystrophy
  • TSH level - Often mildly elevated (4-10 IU/L) due to lack of cortisol's inhibitory effect 2

Monitoring Tests During Follow-up

  • Electrolytes (sodium, potassium) - For mineralocorticoid dosing
  • Blood pressure (supine and standing) - For both glucocorticoid and mineralocorticoid adequacy
  • Screening for associated autoimmune diseases, particularly thyroid disease 1

Critical Management Point

If adrenal crisis is suspected, never delay treatment for diagnostic testing 1. Administer IV hydrocortisone immediately at stress doses (100 mg bolus, then 50-100 mg every 6-8 hours) before any test results return 1. You can draw cortisol and ACTH before giving hydrocortisone, but do not wait for results. If you must give steroids before drawing labs, use dexamethasone (does not interfere with cortisol assays) 4.

The Endocrine Society guidelines emphasize that diagnostic testing should have a low threshold in acutely ill patients with unexplained symptoms, as early diagnosis prevents progression to life-threatening crisis and improves long-term quality of life 1.

References

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