QuestionSBA
QuestionChoice
Pseudo-Cushing's syndrome is thought to be caused by decreased clearance of cortisol by the liver leading to excess serum cortisol. In Pseudo-Cushing's syndrome, high-dose dexamethasone acts on the intact hypothalamus-pituitary-adrenal axis to reduce both ACTH and cortisol.
10024229
e
Pseudo-Cushing's Syndrome due to alcohol
QuestionChoice
Exogenous corticosteroid use results in a raised cortisol which is completely independent from the hypothalamus-pituitary-adrenal axis. Therefore dexamethasone, which acts on this axis, does not affect cortisol levels.
10024228
d
Exogenous corticosteroid use
QuestionChoice
This is incorrect as ectopic sources of ACTH, such as lung cancers, are independent of BOTH the hypothalamus and pituitary. These sources will produce excess ACTH which will act on the adrenals resulting in excess cortisol production. As dexamethasone only acts centrally on the hypothalamus and not on the ectopic source of ACTH, it will not suppress serum ACTH or cortisol levels.
10024227
c
Ectopic ACTH production
QuestionChoice
This is incorrect as dexamethasone will act on the pituitary to suppress ACTH production. This will, by extension, suppress cortisol production from the adrenals.
10024226
b
Pituitary adenoma
QuestionChoice
In patients with adrenal adenomas, cortisol production is independent from the pituitary as the excess production is derived from the adrenals. Therefore, even though dexamethasone will suppress the pituitary (resulting in low ACTH), cortisol levels will remain high due to the ectopic production from the adrenals.
10024225
a
Adrenal adenoma
Concept
Chapter
2693
3764
Cushing's syndrome
Topic
133
Endocrinology
17243
A 50-year-old female experiencing weight gain, excessive hair growth and proximal muscle wasting is referred to an endocrinologist for suspected Cushing’s syndrome. A high-dose dexamethasone test is performed which reveals a suppressed ACTH and a high cortisol level.

Which of the following is the most likely cause of this patient's Cushing’s syndrome?
a