A lab pattern suggesting a corticotropin-secreting pituitary adenoma is which of the following?

A lab pattern suggesting a corticotropin-secreting pituitary adenoma is which of the following?

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

Answer: (C)

In this situation, the pituitary tumor makes excess ACTH, which continuously stimulates the adrenal cortex to produce cortisol. Because the source of ACTH is the pituitary tumor and not the adrenal gland, the elevated ACTH drives cortisol up, so both rise. This pattern—high ACTH with high cortisol—fits a corticotropin-secreting pituitary adenoma. If ACTH were high but cortisol low, that would suggest adrenal underfunction or other atypical signaling, not a corticotropin-secreting tumor. If ACTH were low with high cortisol, that points to an ACTH-independent source of cortisol, such as an adrenal tumor. If both were low, it would indicate adrenal insufficiency or a failure of the pituitary-adrenal axis.

In this situation, the pituitary tumor makes excess ACTH, which continuously stimulates the adrenal cortex to produce cortisol. Because the source of ACTH is the pituitary tumor and not the adrenal gland, the elevated ACTH drives cortisol up, so both rise. This pattern—high ACTH with high cortisol—fits a corticotropin-secreting pituitary adenoma.

If ACTH were high but cortisol low, that would suggest adrenal underfunction or other atypical signaling, not a corticotropin-secreting tumor. If ACTH were low with high cortisol, that points to an ACTH-independent source of cortisol, such as an adrenal tumor. If both were low, it would indicate adrenal insufficiency or a failure of the pituitary-adrenal axis.