Conn's syndrome

Question 1

Definition of Conn’s syndrome

Answer 1

Primary hyperaldosteronism due to aldosterone-producing adrenal adenoma. Aldosterone is produced in excess independent of the RAAS so plasma renin will be low so aldosterone:renin ratio will be high.

Question 2

Causes of hyperaldosteronism

Answer 2

Primary hyperaldosteronism = adrenal gland produces excess aldosterone independent of RAAS
- 2/3 due to an adrenal adenoma = Conn’s syndrome
- 1/3 due to bilateral adrenocortical hyperplasia (more cells in zona glomerulosa can secrete aldosterone)
Secondary hyperaldosteronism = high renin causes high aldosterone. High renin release is due to low renal perfusion due to:
- renal artery stenosis
- diuretic use
- congestive heart failure

Question 3

Pathophysiology

Answer 3

High aldosterone results in increased Na+ & H20 reabsorption & K+ excretion & increased H+ excretion. High plasma volume results in secondary hypertension. Renin release from JGA cells of afferent arteriole is inhibited. = high aldosterone, low renin.

Aldosterone:
- increases activity of H+ ATPase pump in apical membrane of alpha intercalated cells in collecting ducts –> more H+ excretion
- increases transcription of ENaC in apical membrane & activity of basolateral Na+/K+ ATPase in principal cells of collecting ducts -> Na+ & water rebabsorption

Question 4

Signs & symptoms

Answer 4

Refractory hypertension (not controlled with 3 or more BP drugs)
Headaches
Due to hypokalemia: muscle weakness, paraesthesia, polyuria, polydipsia

Question 5

Investigations & diagnosis
- 1st line + diagnostic
- + gold standard test to determine the cause

Answer 5

1st line
- U & E- high Na+, low K+
- Plasma aldosterone: renin ratio - high as aldosterone is high & renin is low
- ECG shows hypokalemia.
- **Gold standard= Fludrocortisone suppression test **(fludrocortisone is a mineralocorticoid & should suppress aldosterone levels in healthy people, failure of aldosterone suppression indicates primary hyperaldosteronism) or IV saline infusion testing (IV 0.9% NaCl should suppress aldosterone in healthy people as there is sufficient salt so no more Na+ needs to be reabsorbed, failure of aldosterone suppression indicates primary hyperaldosteronism)
- Gold standard = adrenal venous sampling- differentiates bilateral adrenocortical hyperplasia from unilateral adrenal adenomas as the cause of primary hyperaldosteronism.

Then:
Adrenal CT/MRI- to locate adrenal adenoma

Question 6

Management for primary hyperaldosteronism

Answer 6

For unilateral adrenal adenomas =
1st line = laparoscopic adrenalectomy to remove adrenal adenoma + aldosterone antagonist (Spironolactone, Eplerenone) 4 weeks pre-operatively to increase K+ & lower BP to reduce bleeding during surgery.
2nd line (if surgery unsuitable) = aldosterone antagonists (Spironolactone, Eplerenone- cause K+ levels to increase)

For bilateral adrenocortical hyperplasia or bilateral adrenal adenomas=
1st line = aldosterone antagonist (Spironolactone)

Question 7

Management for secondary hyperaldosteornisms

Answer 7

Secondary hyperaldosteronism occurs due to renal hypoperfusion causing high renin release which stimulates excess aldosterone release. TREAT UNDERLYING CAUSE:
Renal artery stenosis- percutaneous renal artery angioplasty via femoral artery
Diuretics- stop diuretics
Congestive heart failure- Ace-i & beta blocker with furosemide, then add Spironolactone then consider CRT/Digoxin

Question 8

Complications of excess aldosterone

Answer 8

Hypokalemia- leads to arrythmias
Metabolic alkalosis- as too much H+ excreted in urine