Cushing syndrome

Question 1

etiology ACTH dependent causes of cushing syndrome ?

Answer 1

ACTH dependent causes
Cushing’s disease (80%): pituitary tumour secreting ACTH producing adrenal hyperplasia
ectopic ACTH production (5-10%): e.g. small cell lung cancer is the most common causes

Question 2

ACTH independent causes

Answer 2

iatrogenic: steroids

adrenal adenoma (5-10%)

adrenal carcinoma (rare)

Carney complex: syndrome including cardiac myxoma
micronodular adrenal dysplasia (very rare)

Question 3

Pseudo-Cushing’s

Answer 3

mimics Cushing’s

often due to alcohol excess or severe depression

causes false positive dexamethasone suppression test or 24 hr urinary free cortisol

Question 4

how to differentiate between cushing and pseudo cushing ?

Answer 4

insulin stress test may be used to differentiate

used in investigation of hypopituitarism

Question 5

how to do insulin stress test ?

Answer 5

IV insulin given, GH and cortisol levels measured
with normal pituitary function GH and cortisol should rise

Question 6

x

Question 7

x

Question 8

x

Question 9

x

Question 10

x

Question 11

x

Question 12

x

Question 13

what are the general findings consistent with cushing syndrome

Answer 13

hypokalemic metabolic alkalosis

ectopic ACTH secretion is characteristically associated with very low potassium

Question 14

x

Question 15

x

Question 16

what are the tests to confirm cushing syndrome

Answer 16

overnight dexamethasone test

Question 17

how to localise with overnight dexamethasone test

Answer 17

CORTSIOL NOT SUPRESSED but ACTH suppressed - then cushing syndrome originating from adrenal adenoma

CORTISOL SUPRESSED and ACTH suppressed - then pituitary

if CORTISOL NOT SUPPRESED AND ACTH NOT SUPRRESED then ectopic ACTH - such as small cell lung cancer