Cushing's Syndrome

I would be keen to examine this lady's blood pressure and dipstick the urine for evidence of overt glycosuria and proteinuria. I also would like to complete my examination by checking the visual fields and performing a funduscopy to look for evidence of retinopathy and papilloedema. A history of steroid usage is of prudent importance in this patient.

This lady has Cushing's syndrome as evidenced by the presence of moon-face associated with hirsutism and acne. There are buffalo hump and truncal obesity as well. There is thinning of the skin with localised bruises especially over the cubital fossae of both arms. However there is no purplish striae noted on the abdomen and inner thighs. There is no oral thrush. Patient has proximal weakness. The back is straight with no features of kyphoscoliosis.

Questions:
1. What are the causes of Cushing's syndrome?
Outline: Pituitary-driven, adrenal and ectopic or iatrogenic sources.

2. How would you investigate to determine the cause?

I would screen the patient by doing a 24hr urinary free cortisol first and overnight dexamethasone suppression test. A high dose dexamethasone suppression test is then needed to localise the source of excess cortisol. An elevated ACTH level would isolate the source to either from pituitary or ectopic source.

3. What are the other tests to determine the source of ACTH (to distinguish primary from ectopic)?

CRH and inferior petrosal sinus sampling. An MR of the pituitary gland is helpful as well.

4. How would you manage Cushing's syndrome?

Outline: If possible, the underlying source of excess cortisol should be removed. In cases where the source cannot be removed, I would manage the complications which may arise from Cushing's syndrome.

5. What is Nelson's syndrome?

(A reminder: In real exam situation, you are unlikely to get so far. If you do, then there are 2 extreme possibilities, ie, either you score tremendously..or you failed badly!)

The bell has already rang! The answer is in the book :)