Endocrinology: Cushings Syndrome

Question 1

What is cortisol?

Answer 1

Most abundant corticosteroid - 95% glucocorticoid activity

From the zona fasiculata - in response to ACTH

-ve feedback = decreased CRH (HT) + ACTH (AP)

Actions =

• Increased protein breakdown
• Increased gluconeogenesis
• Increased lipolysis - redistribution

Question 2

What is cushings syndrome?

Answer 2

Chronic excessive exposure to cortisol

Question 3

What are the causes of cushings syndrome?

Answer 3

1. EXOGENOUS = prescribed glucocorticoids
2. ENDOGENOUS
   - Cushings disease = benign pituitary adenoma secreting ACTH
   - Adrenal cushings = adrenal tumour secreting excess cortisol
   - Non-pituitary tumour (ectopic) = SCLC producing ACTH/CRH

Question 4

What are the signs and symptoms of cushings syndrome?

Answer 4

Plethoric

Moon shaped face

Buffalo hump

Abdominal obesity

Purple abdo striae

Acute weight gain

Hyperglycaemia

Hypertension

Question 5

How should cushings syndrome be investigated?

Answer 5

1. Low dose dexamethasone suppression test
   - Normal (ACTH dep) = suppression
   - Exogenous (ACTH dep) = suppression
   - Endogenous (ACTH indep) = no suppression
2. High dose dexamethasone suppression test
   - Benign pituitary adenoma (ACTH dep) = suppression
   - Adrenal adenoma (ACTH indep) = no suppression
   - Ectopic (ACTH dep) = no suppression
3. Measure ACTH
   - Adrenal adenoma (ACTH indep) = low
   - Ectopic (ACTH dep) = high

Question 6

How should cushings syndrome be managed?

Answer 6

Iatrogenic = stop medication if possible

Cushings disease (benign pituitary adenoma secreting ACTH) = removal of pit adenoma

Adrenal cushings (adrenal tumour secreting excess cortisol) = adrenalectomy, radiotherapy, adrenolytic drugs

Non-pituitary tumour (SCLC producing ACTH/CRH) = surgery, radiotherapy, chemo