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Incidental adrenal mass — ABIM Board MCQ

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ModerateGeneral Internal MedicineIncidental adrenal massABIM Board

A 61-year-old woman undergoes noncontrast abdominal CT for renal colic. Imaging reveals a 2.5-cm homogeneous left adrenal mass with an attenuation of 6 Hounsfield units. She has hypertension and well-controlled type 2 diabetes mellitus. Her serum potassium level is normal, and she has no proximal muscle weakness, easy bruising, or violaceous striae. Which of the following is the most appropriate initial test to screen this adrenal incidentaloma for autonomous cortisol secretion?

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Correct answer: B — Perform an overnight 1-mg dexamethasone suppression test

The correct answer is B. Adrenal incidentalomas should be screened for autonomous cortisol secretion with an overnight 1-mg dexamethasone suppression test, even when there are no overt Cushingoid findings. A post-dexamethasone morning cortisol level of 1.8 micrograms/dL or less indicates appropriate suppression; failure to suppress suggests mild autonomous cortisol secretion. Hypertension and diabetes are relevant cortisol-associated comorbidities. Twenty-four-hour urinary free cortisol and late-night salivary cortisol are useful tests for overt Cushing syndrome but can be normal in mild autonomous cortisol secretion and are not the preferred initial tests in this setting. Immediate adrenalectomy is not indicated for a 2.5-cm homogeneous, lipid-rich lesion and should not precede biochemical evaluation. Benign imaging characteristics do not establish that an adrenal mass is hormonally inactive.

Reference: Fassnacht M, et al. European Society of Endocrinology clinical practice guidelines on the management of adrenal incidentalomas, section on assessment of hormone excess. European Journal of Endocrinology. 2023;189:G1-G42. https://pubmed.ncbi.nlm.nih.gov/37318239/