A 48-year-old hypertensive woman has bilateral adrenal incidentalomas (2.3 cm and 1.8 cm), serum cortisol 3.2 µg/dL post 1 mg overnight dexamethasone suppression test, and an aldosterone-to-renin ratio of 42 (ng/dL per ng/mL/h). Her ACTH is suppressed. She has type 2 diabetes and osteopenia. What is the most accurate diagnosis and next best step?
- A Bilateral adrenal hyperplasia causing primary aldosteronism; adrenal vein sampling
- B Non-functioning bilateral adenomas; repeat imaging in 12 months
- C Mild autonomous cortisol secretion (MACS) with concomitant primary aldosteronism; adrenal vein sampling ✓
- D Adrenocortical carcinoma; surgical resection
Explanation
Post-dexamethasone cortisol 1.8–5.0 µg/dL with suppressed ACTH meets criteria for MACS (mild autonomous cortisol secretion), linked to hypertension, diabetes, and osteopenia in this patient. An elevated aldosterone-to-renin ratio of 42 satisfies screening threshold for primary aldosteronism (>30 in most guidelines). Both diagnoses therefore coexist. Adrenal vein sampling (AVS) is needed to determine lateralisation of aldosterone excess before considering unilateral adrenalectomy. Non-functioning adenomas would require normal function tests; ACT carcinoma criteria (size > 4 cm, CT HU > 10, loss of chemical shift on MRI) are not met.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.