Hypertension

Question 1

What’s resistant HTN?

Answer 1

BP 140/90 despite 3 antihypertensives including a diuretic

Question 2

DDx resistant HTN

Answer 2

Non-compliance
ETOH +++
OSA
Primary aldosteronism (20% resistant HTN)
Cushing's 
Renal insufficiency 
Pheochromocytoma (very rare)
Renal artery stenosis

Question 3

When and how do you check renin and aldosterone in resistant HTN?

Answer 3

Preferably morning
Check electrolytes at the same time because hypokalaemia can lower aldosterone production

Renin <10ng/ml is suppressed; If renin is suppressed, aldosterone should be 0
Don’t need to look at ratio

If renin is suppressed and aldosterone >15, this confirms the diagnosis of primary aldosteronism; 10-15 is equivocal

Question 4

Explain RAS in volume expansion and volume depletion

Answer 4

Volume expansion –> kidney senses and stops making renin –> stops making aldosterone

Volume depleted –> kidney makes renin –> renin coverts angiotensinogen to angiotensin I –> angiotensin I gets converted to II by ACE –> angiotensin II is a direct vasoconstrictor and also stimulates aldosterone production by the adrenal gland –> aldosterone stimulates reabsorption of water and sodium, and excretion of potassium in DCT

Question 5

How do antihypertensives affect renin?

Answer 5

Antihypertensives work by vasodilator or volume depletion

Both will cause kidneys make renin

Question 6

When to think of pheochromocytoma?

Answer 6

Incidental adrenal nodule

Heart failure in young person without risk factors

Question 7

Workup of resistant HTN

Answer 7

Aldosterone
Renin
Potassium 
Sleep study
Renal Doppler US 
24h urine cortisol or midnight salivary cortisol
Serum metanephrine/normetanephrine

Question 8

What is cortisol?

Answer 8

Catabolic hormone

Breaks down muscle, protein and fat

Question 9

Whats the dexamethasone suppression test?

Answer 9

Take 1mg dexamethasone between 11pm-midnight then check morning serum cortisol by 0830

Cortisol should be <1.8microg/dL

To test for adrenal Cushing’s

Question 10

Can we diagnose pheochromocytoma if plasma metanephrines and normetanephrines are positive?

Answer 10

Plasma metanephrines and normetanephrines need to be x3-10 ULN

Clinical clues include incidentaloma (adrenal), HF in young person without risk factors

Question 11

What does potassium do to aldosterone?

Answer 11

Hypokalaemia lowers aldosterone production, hyperkalaemia increases aldosterone production