Perform dexamethasone suppression test in PA patients with adrenal adenoma

STEP 1 — Gather Information

Confirm PA diagnosis and adrenal adenoma on cross-sectional imaging; review medications for CYP3A4 inducers (e.g., anticonvulsants, rifampin) or agents affecting dexamethasone metabolism; check serum potassium and baseline cortisol if available; ensure patient can comply with overnight fasting and oral dexamethasone administration.
Action: If eligible, proceed to administer the dexamethasone suppression test.

STEP 2 — Rule In / Rule Out

Administer 1 mg dexamethasone orally between 23:00 and 24:00; draw serum cortisol at 08:00–09:00 the next morning.
Decision: If serum cortisol >1.8 μg/dL (50 nmol/L), rule in autonomous cortisol secretion (ACS); if ≤1.8 μg/dL, rule out ACS.

STEP 3 — Classify or Stratify

If ACS is ruled in, order confirmatory tests: 24-hour urinary free cortisol and midnight salivary cortisol; consider plasma metanephrine during adrenal venous sampling if AVS is planned for PA subtyping.
Action: Initiate follow-up testing to characterize cortisol excess severity.

STEP 4 — Decide

If follow-up tests confirm ACS, plan for perioperative stress-dose glucocorticoids due to risk of postoperative adrenal insufficiency; if ACS is ruled out, proceed with PA management per guideline (e.g., mineralocorticoid receptor antagonist or adrenalectomy).
Decision: Tailor surgical or medical approach based on cortisol secretion status.

Clinical Guardrails / Mimics / Pitfalls

Do not rely solely on the dexamethasone suppression test for Cushing syndrome diagnosis; false positives may occur with oral estrogen, obesity, major depression, alcohol use, or acute illness. False negatives are rare but possible with dexamethasone malabsorption, CYP3A4 inducers, or incorrect dosing. Do not use test results to direct PA-specific therapy; its role is to evaluate autonomous cortisol secretion only. Avoid testing in patients unable to comply with overnight protocol or with known dexamethasone hypersensitivity.

Concrete Clinical Example

A 48-year-old man with PA and a 1.1 cm right adrenal adenoma on CT undergoes dexamethasone suppression test; serum cortisol next morning is 2.0 μg/dL (>1.8). Follow-up 24-hour urinary free cortisol is 120 μg/24h (elevated) and midnight salivary cortisol is 1.2 μg/dL (high). He is diagnosed with mild autonomous cortisol secretion. Prior to laparoscopic adrenalectomy, he receives stress-dose hydrocortisone perioperatively.

Source: Primary Aldosteronism: An Endocrine Society Clinical Practice Guideline, Endocrine Society, 2025, https://doi.org/10.1210/clinem/dgaf284