Primary aldosteronism is the most frequent form of secondary hypertension accounting for up to 5-10% of all hypertensive patients and it is caused by bilateral idiopathic hyperplasia in approximately two-thirds of cases and aldosterone-producing adenoma (Conn's syndrome) in one-third.

In rare cases primary hyperaldosteronism is due to unilateral adrenal hyperplasia or glucocorticoid-remediable aldosteronism (familial form).

In its classical form, primary aldosteronism presents with aldosterone excess, low plasma renin activity and hypokalemia, but several reports indicate that normokalemic primary aldosteronism is the most common presenting sign of the disease. Patients with aldosterone producing adenomas have more severe hypertension, more frequent hypokalemia, higher plasma and urinary levels of aldosterone, and are younger than those with bilateral hyperplasia.

A valid screening test for the disease is the measurement of the plasma aldosterone concentration to plasma rennin activity ratio taken when the patient is in upright position; the ratio is typically increased in primary aldosteronism. A suppression dynamic test (fludrocortisone, saline infusion, oral salt-loading, and captopril test) is usually performed after a positive screening test to confirm inappropriately high plasma aldosterone levels. Once primary aldosteronism is confirmed, the subtype needs to be determined to guide treatment. Computed tomography or magnetic resonance imaging are required to detect the adenoma. If the studies are inconclusive, with dubious adrenal imaging features, patients should be considered for adrenal vein sampling.

Optimal treatment for aldosterone-producing adenoma or unilateral hyperplasia is unilateral laparoscopic adrenalectomy. The idiopathic bilateral hyperplasia and glucocorticoid-remediable aldosteronism subtypes should be treated pharmacologically (mineralocorticoid receptor antagonist and dexamethasone respectively).

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