Which tumor is listed as an ectopic ACTH-secreting source in Cushing syndrome?

Which tumor is listed as an ectopic ACTH-secreting source in Cushing syndrome?

• A. Small cell lung cancer
• B. Prostate adenocarcinoma
• C. Hepatocellular carcinoma
• D. Basal cell carcinoma

Answer: (A)

Ectopic ACTH production occurs when a nonpituitary tumor independently secretes ACTH, driving the adrenal cortex to excess cortisol and causing Cushing syndrome. The classic source is a neuroendocrine tumor of the lung, particularly small cell carcinoma, because these tumors autonomously produce ACTH regardless of hypothalamic-pituitary signals. This leads to elevated ACTH and cortisol with features like hypertension, hyperglycemia, hypokalemia, and metabolic alkalosis, and typically poor suppression on high-dose dexamethasone testing. The other tumors listed do not commonly secrete ACTH ectopically, so they aren’t the usual sources of ectopic ACTH syndrome.

Ectopic ACTH production occurs when a nonpituitary tumor independently secretes ACTH, driving the adrenal cortex to excess cortisol and causing Cushing syndrome. The classic source is a neuroendocrine tumor of the lung, particularly small cell carcinoma, because these tumors autonomously produce ACTH regardless of hypothalamic-pituitary signals. This leads to elevated ACTH and cortisol with features like hypertension, hyperglycemia, hypokalemia, and metabolic alkalosis, and typically poor suppression on high-dose dexamethasone testing. The other tumors listed do not commonly secrete ACTH ectopically, so they aren’t the usual sources of ectopic ACTH syndrome.