What is the expected result of an overnight dexamethasone suppression test in primary hypercortisolism?

• A. Suppressed
• B. Unsuppressed
• C. Partially suppressed
• D. Not performed

Answer: (B)

The test checks whether cortisol production can be shut down by negative feedback from dexamethasone. In a healthy person, giving a small dose at night suppresses ACTH and reduces morning cortisol. In primary hypercortisolism, the adrenal gland makes cortisol autonomously, so cortisol remains high despite the dexamethasone. Therefore, the expected result is unsuppressed cortisol in the morning (not reduced to normal low levels).