QuestionSBA
QuestionChoice
This is not the correct answer. While this is a good test to determine whether it is Cushing's disease (Pituitary source), a more ideal investigation would be to start with a low-dose dexamethasone suppression test to confirm cortisol excess. Lack of suppression with low dose suggests Cushing's syndrome such as exogenous steroid use or cortisol producing adrenal adenoma, lack of suppression with low dose but suppression with high dose suggests Cushing's disease, and lastly, lack of suppression by both low or high dose suggests ectopic ACTH source such as an ACTH producing tumour.
10027308
c
High-dose dexamethasone suppression test
QuestionChoice
This is not the correct answer. While it is a useful follow-up investigation to localize tumour(s) that may be secreting ACTH or cortisol, it is important to confirm cortisol excess with preliminary diagnostic investigations first.
10027309
d
CT chest and abdomen
QuestionChoice
This is not the correct answer. While it is a useful follow-up investigation to localize an ACTH-secreting pituitary tumour (Cushing's disease), it is important to confirm cortisol excess with preliminary diagnostic investigations first.
10027310
e
MRI of the Pituitary
QuestionChoice
This is not the correct answer. While this is a good test to localise the source of cortisol excess by determining whether it is ACTH-dependent or ACTH-independent causes.
10027307
b
Plasma ACTH levels
QuestionChoice
This is the correct answer. The clinical presentation of this patient suggests cortisol excess. As such, to determine cortisol excess, a positive result must be obtained from 2 of the following 3 investigations; Late-night salivary cortisol, 24-hour urinary free cortisol, and a low-dose dexamethasone suppression test.
10027306
a
Late-night salivary cortisol
Concept
Chapter
2693
3764
Cushing's syndrome
Topic
133
Endocrinology
17859
A 40-year-old man presents with weight gain around his truncal area, stretch marks on his stomach and bruises on his limbs despite having no recollection of injury. He has a past medical history of asthma and is on daily prednisolone.

What is the most appropriate first-line investigation to carry out?
a