Cushing's Syndrome

Question 1

What is Cushing’s Syndrome?

Answer 1

Symptoms related to prolonged cortisol excess

Question 2

What actions does cortisol have?

Answer 2

• Immune inhibition
• Inhibits bone formation
• Raises blood glucose
• Increases metabolism
• Increases alertness

Question 3

What can a high cortisol cause?

Answer 3

• HTN and cardiac hypertophy
• Hyperglycaemia
• Depression and insomnia

Question 5

What are the symptoms of Cushing’s?

Answer 5

Round in the middle with thin limbs:

• Central Obesity
• Round ‘moon’ face
• ‘Buffalo hump’ (fat pad on neck)
• Abdominal striae
• Limb muscle wasting

Question 6

What else may occur in Cushing’s?

Answer 6

• Osteoporosis

- Easy bruising/poor wound healing

Question 6

What can cause Cushing’s?

Answer 6

• Exogenous steroids
• Cushing’s disease (pituitary adenoma, releasing ACTH)
• Adrenal adenoma (cortisol produced in adrenals)
• Paraneoplastic Cushing’s

Question 7

What is paraneoplastic Cushing’s?

Answer 7

• Excess ACTH released from a cancer that’s not in the pituitary (ectopic ACTH)

Question 8

What is the most common cause of paraneoplastic Cushing’s?

Answer 8

Small cell carcinoma of the lung

Question 9

What test is used to diagnose Cushing’s?

Answer 9

Dexamethasone suppression test

Question 10

What is the dexamethasone suppression test?

Answer 10

1. Give patient 1mg dexamethasone at night (e.g. 10pm)
2. Measure ACTH and Cortisol in the morning (e.g. 9am)
3. Normal=cortisol should be low (cortisol is normally high in the morning, so dexamethasone inhibits this)

Question 11

What are the two parts to the dexamethasone suppression test?

Answer 11

1. Low dose (1mg, if negative, Cushing’s excluded)

2. High dose (8mg, differentiates cause)

Question 12

What happens in the high dose test if it’s a pituitary adenoma?

• Cortisol
• ACTH

Answer 12

Cortisol- suppressed (low)

ACTH- suppressed (low)

Question 13

What happens in the high dose test if it’s an adrenal adenoma?

• Cortisol
• ACTH

Answer 13

Cortisol- not suppressed (high)

ACTH- suppressed (low)

Cortisol independent of ACTH

Question 14

What happens in the high dose test if it’s ectopic ACTH e.g. small cell lung carcinoma ?

• Cortisol
• ACTH

Answer 14

Cortisol- not suppressed (high)

ACTH- not suppressed (high)

Cortisol increased by ectopic ACTH

Question 15

What alternative is there to dexamethasone suppression tests?

How does it work?

Answer 15

24 hour urinary free cortisol

Patient collects all their urine over a 24hr period for a cortisol level (usually in a big container)

Question 16

What are the issues with 24hr urinary free cortisol?

Answer 16

• Cumbersome and not nice

- Does not indicate underlying cause

Question 17

What may UsEs show in Cushing’s?

Answer 17

Potassium may be low in an adrenal adenoma due to aldosterone release

Question 18

How is Cushing’s treated?

Answer 18

Surgical removal of any tumour:

• Pituitary
• Adrenal
• Small cell lung carcinoma

Question 19

What alternative is there if tumour removal isn’t an option?

Answer 19

• Remove both adrenal glands

- Give the patient replacement hormones for life