Y2 ENDOCRINE TESTS

Question 1

to investigate if adrenal insufficiency?

Answer 1

short synacthen test

Question 2

how do you perform a short synacthen test?

Answer 2

• measure plasma cortisol
  before test.

–> IV/IM ACTH

• measure plasma 30 minutes after.

Question 3

what is a normal ACTH baseline?

Answer 3

> 250nmol/L

Question 4

what should cortisol be normally after ACTH injection

Answer 4

> 550nmol/L

Question 5

what will happen in the synacthen test if the patient has adrenal insufficiency?

Answer 5

cortisol will remain low despite ACTH injection.

Should not rise above >550nmol/L after 30 min or increase by >200nmol/L.

Question 6

what will happen to levels in the synacthen test if the patient has adrenal insufficiency?

Answer 6

• very high ACTH.
• low cortisol.
• high renin.
• low aldosterone.

Question 7

how do you diagnose cushing’s?

Answer 7

1. overnight dexamethasone suppression test.
2. 24hour urinary free cortisol.
3. late night salivary cortisol.
4. low dose dexamethasone suppression test.

repeat to confirm.

Question 8

what results of an overnight dexamethasone test will be seen in Cushing’s?

Answer 8

plasma cortisol >50nmol/L.

Question 9

what results of a 24 hour urine free cortisol will be seen in Cushing’s?

Answer 9

elevation

Question 10

what results of a low dose dexamethasone suppression test would indicate cushing’s?

Answer 10

no suppression.

if there is suppression it suggests another cause e.g. depression, obesity, alcohol abuse.

Question 11

following a failure of cortisol to suppress after a low dose dexamethasone suppression test, what would be the next step?

Answer 11

imaging/investigation for pituitary adenoma or ectopic source of ACTH.

Question 12

test to diagnose primary aldosteronism?

Answer 12

aldosteron to renin ratio.

Question 13

if suspicion of primary aldosteronism and ARR is raised, what is the next step?

Answer 13

saline suppression test

Question 14

what confirms primary aldosteronism?

Answer 14

failure of plasma aldosterone to suppress by >50% with 2 litres of saline

Question 15

how do you confirm subtype of primary aldosteronism?

Answer 15

• adrenal CT to check for adenoma or bilateral adrenal hyperplasia.

?- adrenal vein sampling to confirm adenoma is true source of excess aldosterone - only sometimes check?

Question 16

how do you diagnose congenital adrenal hyperplasia?

Answer 16

basal or stimulated 17-OH progesterone.

Question 17

how do you investigate phaeochromocytoma initially?

Answer 17

• urinary 24 hour catecholamines or metanephrins.
• plasma catecholamine (ideally when symptomatic).

note it is episodic catecholamine secretion therefore urine and plasma levels may be normal.

Question 18

how do you confirm phaeochromocytoma once catecholamine excess has been established?

Answer 18

MRI scan (abdo. or whole body).

• MIBG
• PET

Question 19

when might phaeochromocytoma levels of catecholamine be low?

Answer 19

• if malignant or extra-adrenal as they are less efficient at catecholamine synthesis.
• catecholamine excretion is episodic.

Question 20

investigation of hypercalcaemia?

Answer 20

PTH

Question 21

Low/normal albumin +
- suppressed PTH
- high phosphate
suggests?

Answer 21

bone pathology

Question 22

Low/normal albumin +

• high/normal PTH
• low/normal phosphate
• reduced urine Ca2+ suggests?

Answer 22

familial hypocalciuric hypercalcaemia (FHH)

Question 23

Low/normal albumin +

• high/normal PTH
• low/normal phosphate
• increased urine Ca2+ suggests?

Answer 23

primary or tertiary hyperparathyroidism

Question 24

• hypercalcaemia
• raised albumin
• raised urea
  suggests?

Answer 24

dehydration

Question 25

Low/normal albumin +
- suppressed PTH
- high phosphate 
\+ high alk. phosphatase (ALP)
suggests?

Answer 25

• bone mets
• sarcoidosis
• thyrotoxicosis

Question 26

Low/normal albumin +
- suppressed PTH
- high phosphate 
\+ low alk. phosphatase (ALP)
suggests?

Answer 26

• myeloma.
• vit. D excess
• mild alkali syndrome (thyrotoxicosis, sarcoidosis, raised HCO3)

Question 27

• hypercalcaemia
• raised ALP
• suppressed PTH
  suggests?

Answer 27

malignancy

Question 28

how do you diagnose hypercalcaemia of malignancy?

Answer 28

• x-ray, CT, MRI

- isotope bone scan

Question 29

how do you image the parathyroid glands?

Answer 29

sestamibi scan

Question 30

• raised PTH

- raised Ca2+

Answer 30

primary or tertiary hyperparathyroidism

Question 31

• low Ca2+

- raised PTH

Answer 31

secondary hyperparathroidism

Question 32

how do you diagnose Paget’s disease?

Answer 32

• x-ray
• isotope bone scan shows distribution across body
• raised ALP and normal liver function test