Hyperaldosteronism

Question 1

Top tip: Hyperaldosteronism is worth remembering as the most common cause of?

Answer 1

secondary hypertension

If you have a patient with a high blood pressure that is not responding to treatment consider screening for hyperaldosteronism with a renin:aldosterone ratio. One clue that could prompt you to test for hyperaldosteronism might be a low potassium however be aware that potassium levels may be normal.

Question 2

Aetiology of hyperaldosteronism

Answer 2

Primary hyperaldosteronism
- adrenal glands are directly responsible for producing too much aldosterone.Serum renin will be low as it is suppressed by the high blood pressure.

Secondary hyperaldosteronism
- where excessivereninstimulating the adrenal glands to produce morealdosterone. Serum renin will be high.

Question 3

Primary hyperaldosteronism causes

Answer 3

• Bilateral adrenal hyperplasia(most common)
• Anadrenal adenomasecreting aldosterone (known asConn’s Syndrome)
• Familial hyperaldosteronism type 1 and type 2 (rare)
• Adrenal carcinoma (rare)

Question 4

Secondary hyperaldosteronism causes

Answer 4

There are several causes of high renin levels and they occur when the blood pressure in the kidneys is disproportionately lower than the blood pressure in the rest of the body:

- Renal artery stenosis :is a narrowing of the artery supplying the kidney. This is usually found in patients with atherosclerosis, as an atherosclerotic plaque causes narrowing of this vessel similar to the narrowing of the coronary arteries found in angina. This can be confirmed with adoppler ultrasound, CT angiogram ormagnetic resonance angiography (MRA)

- Renal artery obstruction
- Heart failure

Question 5

Pathophysiology of hyperaldosteronism

Answer 5

• In theafferent arteriole in thekidney there are special cells calledjuxtaglomerular cells
• They sense the blood pressure in these vessels. When they sense alow blood pressurein thearteriole
• they secrete a hormone calledrenin
• Thisliver secretes a protein calledangiotensinogen
• Renin acts to convertangiotensinogen toangiotensin I
• Angiotensin I converts toangiotensin II in thelungs with the help ofangiotensin converting enzyme (ACE).
• Angiotensin II stimulates the release of aldosterone from the adrenal glands.

Aldosteroneis amineralocorticoidsteroid hormone. It acts on the kidney to:

• Increase sodium reabsorption from the distal tubule
• Increase potassium secretion from thedistal tubule
• Increase hydrogen secretion from thecollecting ducts

Question 6

Investigation/diagnosis of hyperaldosteronism

Answer 6

• High aldosteroneand low reninindicatesprimary hyperaldosteronism
• High aldosteroneandhigh reninindicatessecondary hyperaldosteronism

Other investigations relating to the effects of aldosterone:

• Blood pressure (hypertension)
• Serum electrolytes (hypokalaemia)
• Blood gas analysis (alkalosis)

If a high aldosterone level is found then investigate for the cause:

• CT / MRI to look for an adrenal tumour
• Renal doppler ultrasound, CT angiogram or MRA for renal artery stenosis or obstruction

Question 7

Treatment of hyperaldosteronism

Answer 7

Aldosterone antagonists

• Eplerenone
• Spironolactone

Treat the underlying cause

• Surgical removal of adenoma
• Percutaneous renal artery angioplastyvia the femoral artery to treat in renal artery stenosis