A 70-year-old female is seen for possible Cushing syndrome. She has new onset diabetes mellitus, weight gain. No exposure to exogenous corticosteroid. Serum cortisol is 248.4 nmol/L (Normal: less than 50 nmol/L) following 1 mg dexamethasone and 24 hours' urine free cortisol is 3 times greater than upper limit of normal level. A plasma adrenocorticotropic hormone (ACTH) is undetectable. Which of the following in the most appropriate next diagnostic test?
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الإجابة: A. CT scan of adrenal glands
Hypercortisolism is already confirmed by two positive screening tests (failed 1-mg dexamethasone suppression + 24-h UFC 3× ULN). An undetectable ACTH means ACTH-independent Cushing's (adrenal adenoma/carcinoma), so the next test is adrenal CT/MRI.
- Late-night salivary cortisol (C) is another screening test — not needed once the diagnosis is established.
- Pituitary MRI (D) and inferior petrosal sinus sampling (B) are for ACTH-dependent disease (high ACTH).
ليش كل خيار صح أو غلط
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A
ليش صح
Undetectable ACTH with high cortisol is the indication for adrenal CT/MRI, which looks for an adrenal adenoma.
✓ 6• Cushing's Syndrome & Disease [Notes].pdf · p. 6 -
C
ليش غلط
Late-night salivary cortisol is one of the three screening tests; two of three (her dexamethasone test and 24-hour urine cortisol) are already positive, which supports Cushing's, so she now needs the cause workup.
✓ 6• Cushing's Syndrome & Disease [Notes].pdf · p. 5 -
D
ليش غلط
Pituitary MRI is for raised ACTH with raised cortisol (Cushing disease, positive CRH or high-dose dexamethasone test); her ACTH is undetectable.
✓ 6• Cushing's Syndrome & Disease [Notes].pdf · p. 6
- المصدر
- 6• Cushing's Syndrome & Disease [Notes].pdf · p. 6
Adrenal gland disorders.pdf · p. 1 - المحاضرة
- Cushing's Syndrome · Endocrinology · Module B
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