Chemical Pathology 6 - Adrenal

Question 1

Recall the 3 zones of the adrenal gland and what is produced in each one

Answer 1

Zone glomerulosa = aldosterone
Zona fasiculata = cortisol
Zona reticularis = androgens

Question 2

What is Schmidt’s syndrome?

Answer 2

Well-known phenomenon in which primary hypothyroidism presents alongside Addison’s disease (primary adrenal failure)

Autoimmune diseases occur more commonly together than by chance

Question 3

What’s the test for Addisson’s, and how should it be performed?

Answer 3

SynACTHen test

Following adminstration of synthetic 250mg ACTH, check cortisol at 30 and 60 mins

Question 4

What is the expected electrolyte abnormality in untreated primary adrenal failure?

Answer 4

Hyponatraemia, hyperkalaemia

Question 5

What are the 3 differentials to consider when a patient with severe hypertension also has an adrenal mass?

Answer 5

1. Phaeochromocytoma (medullary tumour)
2. Conn’s syndrome (aldosterone-secreting tumour - zona glomerulosa)
3. Cushing’s (zona fasciculata tumour secreting cortisol)

Question 6

How should phaeochromocytoma be treated?

Answer 6

Alpha blockers (phenoxybenzamine) THEN beta blockers (to deal with reflex tachycardia)

Question 7

What are the expected aldosterone and renin levels in untreated Conn’s syndrome?

Answer 7

High aldosterone, low renin

Question 8

What are the expected aldosterone and renin levels in untreated Cushing’s syndrome?

Answer 8

Both low

Question 9

What 3 tests can be used to investigate for Cushing’s?

Answer 9

1. 9am cortisol
2. Sneaky midnight cortisol (this is low when normal)
3. Dexamethosone suppression test

Question 10

What does the term ‘cushing’s disease’ refer to?

Answer 10

Cushing’s syndrome that is caused by a pituitary tumour secreting ACTH

Question 11

What is the diagnosis in a patient with symptoms of Cushing’s but a normal result in the low-dose dexamethosone suppression test?

Answer 11

Normal obese person

Question 12

What is the diagnosis in a patient with symptoms of Cushing’s but only a very slightly suppressed cortisol in the low-dose dexamethosone suppression test?

Answer 12

Cushing’s syndrome of indeterminate cause

Question 13

How should Cushing’s syndrome of indeterminate cause be investigated?

Answer 13

Inferior petrosal sinus (pituitary) sampling with CRH stimulation

• Allows us to distinguish Cushing’s disease from ectopic ACTH*
• Since 2008, this is best test - preferred over high dose dexamethasone suppression test and pituitary MRI*

Question 14

If a patient isn’t on steroids, what are the causes of Cushing’s syndrome and what is most common?

Answer 14

Pituitary dependent Cushing’s disease (85%)
Ectopic ACTH
Adrenal adenoma

Question 15

What is the problem with the high dose dexamethasone suppression test?

Answer 15

It only really confirms what we knows - suppression with high dose dexamethasone suggests pituitary Cushing’s disease but that is already the most common cause

Also, it’s wrong 50% of the time when it’s not pituitary Cushing’s disease

Question 16

What is the problem with pituitary MRI?

Answer 16

20% of us will have a non-functioning adenoma appear on the MRI scan

Meanwhile, many Cushing’s patients will have normal MRI scans