What is the typical condition when cortisol levels are low and plasma ACTH levels are elevated?

The correct condition associated with low cortisol levels and elevated plasma ACTH levels is primary adrenal insufficiency, also known as Addison's disease. In this scenario, the adrenal glands are damaged or not functioning properly, leading to insufficient production of cortisol despite the pituitary gland's increased secretion of ACTH in an attempt to compensate for the low cortisol levels.

In primary adrenal insufficiency, the lack of cortisol feedback leads to elevated ACTH levels, since the pituitary gland continues to stimulate the adrenal glands. This is a hallmark of primary adrenal insufficiency, wherein the adrenal cortex fails to respond to ACTH due to its inherent dysfunction.

Other conditions, such as secondary adrenal insufficiency, would typically present with low cortisol levels and low or inappropriately normal ACTH levels due to a failure of the pituitary gland to produce adequate ACTH. An acute adrenal crisis represents a severe and sudden drop in adrenal function, often with accompanying symptoms and may present with very low cortisol and possibly high ACTH too, but it is not characterized as a stable condition. Cushing's syndrome, on the other hand, is marked by elevated cortisol levels, not low, making it unrelated to this scenario.