For which of the following conditions would you expect to see elevation of ACTH?

In the case of an ACTH-producing tumor, commonly known as a corticotroph adenoma or ectopic ACTH-producing tumor, there is an abnormal proliferation of cells that overproduce Adrenocorticotropic Hormone (ACTH). This leads to excess stimulation of the adrenal glands, resulting in increased cortisol production. The high levels of ACTH persist because they are not regulated by the normal feedback mechanisms that would typically suppress ACTH secretion in response to elevated cortisol levels.

This condition contrasts with adrenal insufficiency, where the adrenal glands fail to produce adequate amounts of hormones, leading to an increase in ACTH due to a lack of negative feedback. In primary hyperaldosteronism, the issue is primarily with aldosterone production, which is not directly related to ACTH levels. Secondary adrenal insufficiency, on the other hand, arises when the pituitary gland does not produce enough ACTH, leading to low adrenal function; therefore, you wouldn’t expect elevated ACTH levels.

Thus, an ACTH-producing tumor represents a distinct condition where ACTH levels are elevated due to the pathophysiology of the tumor itself, providing a clear rationale for the choice.