Cushing's

Question 1

What dose the adrenal cortex produce? Pituitary?

Answer 1

Steroid hormones
Zone glomerulosa - mineraocoridoids - aldosterone
zona fasciculatis -glucocorticoids - cortisol
zona reticularis - androgens - sex hormones which have weak effect until peripheral conversion to testosterone and dihydrotestosterone.

CRF from hypothalamus stimulates ACTH release from anterior pituitary which stimulates adrenal cortex to produce cortisol and androgen.

Question 2

What is Cushing’s syndrome? what is it due to?

Answer 2

Clinical state produced by chronic glucocorticoid excess + loss of normal feedback mechanisms of the hypothalamus-pituitary-adreanl axis and loss of circadian rhythm of cortisol secretion (normally highest when waking)

Usually caused by oral steroids
Increased ACTH due to pituitary adenoma (Cushing’s disease)

Question 3

What are causes of Cushing’s syndrome?

Answer 3

ACTH increase:
Cushing’s disease: bilateral adrenal hyperplasia from an ACTH secreting pituitary adenoma.
Ectopic ACTH production - small cell lung cancer and carcinoid tumours (pigmentaion due to increased ACTH, hypokalaemia meatball acidosis due to minerocorticoid activity or cortisol), weight loss, hyperglycaemia)

ACTH independence causes:
Iatrogenic - oral steroid doses
ADreanl adenoma

Question 4

What are symptoms of Cushing’s

Answer 4

Weight gain
Mood change (depression, lethargy, irritability, psychosis)
Proximal weakness
Gonadal dysfunction (irregular menses, hirsutism, erectile dysfunction)
Increases susceptibilty to infection due to immunosuppressive, anti inflammatory and anti allergy effects of cortisol - acne
Achilles tendon rupture recurrent

Question 5

What are signs of Cushing’s?

Answer 5

Central obesity - increased lipogenesis in adipose tissue
Moon face
Buffalo hump
Supraclavicular fat distribution
Skin and muscle atrophy - due to increases proteolysis
Bruises deu to thinning of skin and SC tissue
Abdominal purple striae - catabolic effects on protein structures in skin
OSteoporosis
HTN - due to mineraco corticoid effects of cortisol excess
Hyperglycaemia due to increased hepatic gluconeogenesis with associated polyuria/polydipsia

Signs of cause - abdo mass

Question 6

What test for Cushing’s?

Answer 6

First confirm with tased plasma cortisol
Overnight dexamethasone suppression test
dexamethasone 1mg PO at midnight- do serum cortisol at 8AM
Normally cortisol suppresses to <50nmol/L - no suppression in Cushing’s syndrome.

IF 1st line abnormal - 48h dexamethasone suppression test.

Plasma ACTH - if undetectable, adrenal tumour is likely
- if detectable pituitary tumour vs ectopic aCTH

Question 7

What is the treatment for Cushing’s syndrome?

Answer 7

depends on cause:
Iatrogenic : stop medications if possible
Cushing’s disease - removal of pituitary adenoma
Adrenal adenoma/carincoma - adrenalectomy
ectopic ACTH - surgery if tumour hasn’t spread

Question 8

What is difference between Cushing’s and Addison’s?

Answer 8

Cushing’s :
Hyperglycaemia, weight gain, increased appetite, hypertension, Cushingoid features

Addison's
Hypoglycaemia
Weight loss
Nausea, anorexxia
Hypotension