Which lab pattern would indicate a corticotropin-secreting pituitary adenoma?

Which lab pattern would indicate a corticotropin-secreting pituitary adenoma?

• A. High corticotropin and low cortisol levels
• B. Low corticotropin and high cortisol levels
• C. High corticotropin and high cortisol levels
• D. Low corticotropin and low cortisol levels

Answer: (C)

A corticotroph (ACTH-secreting) pituitary adenoma causes the pituitary to release large amounts of ACTH, whichStimulates the adrenal cortex to produce more cortisol. Because the tumor keeps producing ACTH, cortisol rises even though high cortisol normally suppresses ACTH. So the lab pattern shows both ACTH and cortisol elevated, which is characteristic of ACTH-dependent Cushing disease from a pituitary source. This differs from patterns where cortisol is high but ACTH is low—pointing to an adrenal source or exogenous steroid use, where the adrenals are overproducing cortisol or cortisol is being supplied externally and the pituitary is suppressed. It also differs from a pattern where ACTH is high but cortisol is low, which indicates primary adrenal failure or a problem with the adrenal glands themselves rather than a pituitary tumor.

A corticotroph (ACTH-secreting) pituitary adenoma causes the pituitary to release large amounts of ACTH, whichStimulates the adrenal cortex to produce more cortisol. Because the tumor keeps producing ACTH, cortisol rises even though high cortisol normally suppresses ACTH. So the lab pattern shows both ACTH and cortisol elevated, which is characteristic of ACTH-dependent Cushing disease from a pituitary source.

This differs from patterns where cortisol is high but ACTH is low—pointing to an adrenal source or exogenous steroid use, where the adrenals are overproducing cortisol or cortisol is being supplied externally and the pituitary is suppressed. It also differs from a pattern where ACTH is high but cortisol is low, which indicates primary adrenal failure or a problem with the adrenal glands themselves rather than a pituitary tumor.