Cushing's Syndrome

Question 1

What is Cushing’s syndrome?

Answer 1

The signs and symptoms that develop after prolonged abnormal elevation of cortisol

Question 2

What is Cushing’s Disease?

Answer 2

A pituitary adenoma secretes excessive ACTH –> cushing’s syndrome

Question 3

What are the clinical features of cushing’s syndrome?

Answer 3

Round in the middle with thin limbs:
- moon face
- central obesity
- abdominal striae
- buffalo hump (fat pad on upper back)
- proximal limb muscle wasting
High levels of stress hormone:
- hypertension
- cardiac hypertrophy
- hyperglycaemia (T2DM)
- depression
- insomnia
Other:
- osteoporosis
- easy bruising + poor skin healing

Question 4

What are the causes of Cushing’s syndrome?

Answer 4

Exogenous steroids
Cushing’s disease
Adrenal adenoma
Paraneoplastic cushing’s

Question 5

What is paraneoplastic cushing’s?

Answer 5

Excess ACTH released from a cancer (ectopic ACTH)

Most commonly from a small cell lung cancer

Question 6

How is Cushing’s syndrome diagnosed?

Answer 6

Dexamethasone suppression test

• initially low dose
• if normal response –> cushing’s excluded
• if abnormal –> do high dose test

Question 7

How does the dexamethasone suppression test work?

Answer 7

Patient given dose of dexamethasone at night
Cortisol + ACTH measured in the morning
Tests to see if dexamethasone suppresses their normal morning spike of cortisol

Question 8

How is the low dose dexamethasone suppression test interpreted?

Answer 8

1mg dexamethasone given:

• if cortisol suppressed –> normal result
• if cortisol level not suppressed (high/normal) –> cushing’s syndrome

Question 9

Why is the high dose dexamethasone suppression test done?

Answer 9

To determine whether the cause of cushing’s syndrome is pituitary, adrenal or ectopic

Question 10

How is the high dose dexamethasone suppression test interpreted?

Answer 10

8mg dexamethasone given:

• if cortisol suppressed –> pituitary adenoma (Cushing’s Disease)
• if cortisol is not suppressed but ACTH is suppressed –> adrenal adenoma
• if neither cortisol or ACTH suppressed –> ectopic ACTH

Question 11

What is the main treatment for Cushing’s syndrome?

Answer 11

Remove underlying cause:

• trans-sphenoidal removal of pituitary adenoma
• remove adrenal tumour
• remove tumour producing ectopic ACTH

Question 12

If surgical removal of the cause is not possible, what else can be done?

Answer 12

Remove both adrenal glands + give patient replacement steroid hormones for life