Primary hyperaldosteronism accounts for at least 2% of hypertensive patients. The most common cause is a benign adrenal adenoma, or Conn's syndrome.

INDICATIONS FOR SCREENING

All patients with

1. hypertension resistant to conventional treatment
2. hypertension with associated hypokalaemia in patients not on diuretics.
3. hypertension developing before the age of 30 years

Please refer to Endocrine clinic

INVESTIGATIONS

Screening

Serum potassium	Hypokalaemia is highly suggestive of primary hyperaldosteronism in a hypertensive subject. However, approximately 30% of patients with hyperaldosteronism may be normokalaemic. A low salt diet will often mask hypokalaemia.
24 hour urine potassium excretion	Urinary potassium excretion in excess of 30mmol/24hours following the discontinuation of diuretics and in the presence of hypokalaemia is suggestive of hyperaldosteronism.
Plasma aldosterone: renin ratio	Plasma renin is suppressed in patients with primary hyperaldosteronism, but may also be suppressed in a third of patients with essential hypertension. A high aldosterone:renin ratio is very suggestive of primary hyperaldosteronism.

Confirmatory tests and differentiation of underlying cause

Posture test

Failure of plasma aldosterone to increase (by at least a third above the baseline) is suggestive of an adenoma.

Localisation

Adrenal CT/MR scan

Imaging should only be performed after biochemical confirmation of aldosteronism. Radiological imaging can detect most adenomas >1cm in size. Adrenal carcinoma should be suspected if a tumour of >3cm is found.