Which laboratory finding is most consistent with a diagnosis of Cushing disease?

Which laboratory finding is most consistent with a diagnosis of Cushing disease?

• A. Elevated serum cortisol
• B. Decreased serum cortisol
• C. Elevated calcium
• D. Low serum sodium

Answer: (A)

Cushing disease causes overproduction of cortisol due to a pituitary ACTH-secreting adenoma. Because the underlying issue is too much cortisol, the most consistent lab finding is elevated serum cortisol. This reflects the hypercortisolemia driving the metabolic and vascular changes seen with the condition. The other options don’t fit this pattern: decreased cortisol points to adrenal insufficiency rather than excess cortisol; elevated calcium is not a hallmark of Cushing disease; low serum sodium is not a characteristic feature and doesn’t specifically reflect the cortisol excess.

Cushing disease causes overproduction of cortisol due to a pituitary ACTH-secreting adenoma. Because the underlying issue is too much cortisol, the most consistent lab finding is elevated serum cortisol. This reflects the hypercortisolemia driving the metabolic and vascular changes seen with the condition.

The other options don’t fit this pattern: decreased cortisol points to adrenal insufficiency rather than excess cortisol; elevated calcium is not a hallmark of Cushing disease; low serum sodium is not a characteristic feature and doesn’t specifically reflect the cortisol excess.