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Primary hyperaldosteronism (Conn's syndrome or aldosterone-producing adrenal tumor)

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Diagnosis

Patients suspected of having primary hyperaldosteronismPrimary hyperaldosteronism - a disease where too much aldosterone is being made based on signs, symptoms, or resistant hypertension should be tested. The best screening tests to determine if a patient has primary hyperaldosteronism are simple blood tests that measure the levels of potassium, aldosteroneAldosterone - a mineralocorticoid that controls blood pressure, and renin in the blood. Patients with primary hyperaldosteronism will classically have high aldosterone levels and suppressed renin levels (i.e. very low). They will often also have low potassium levels. If the screening tests suggest primary hyperaldosteronism, then additional testing may be performed to confirm the diagnosis. The confirmatory tests involve trying to suppress (i.e. lower) the amount of aldosterone that is being made by giving the patient a medication through the veins (i.e. IV or intravenous fluid). If the aldosterone levels are still high and the renin levels are still low after these maneuvers, the diagnosis is confirmed. It is important to note that certain high blood pressure medications may interfere with the diagnostic tests and thus, after consultation with a physician, should be discontinued 4 to 6 weeks prior to testing. See below for a more detailed description of each test.

Aldosterone-producing adrenal tumor: Diganosis and Treatment Algorithm for Primary Hyperaldosteronism
Figure 3: Diganosis and Treatment Algorithm for Primary Hyperaldosteronism

Screening test:

PAC:PRA ratio
The first test used in patients suspected to have primary hyperaldosteronism measures the plasma aldosterone concentration (PAC) to plasma renin activity (PRA) ratio. The levels of aldosterone and renin are measured in the blood. A high ratio of PAC to PRA suggests primary hyperaldosteronism; however, additional testing may be needed to confirm the diagnosis.

Confirmatory tests:

Captopril Suppression Test
Captopril is a medication for high blood pressure. A patient is given a single dose of captopril, after which the levels of aldosterone and renin in the blood are measured. In patients with primary hyperaldosteronism, the level of aldosterone in the blood is still high and the level of renin is low even after captopril administration.

24-Hour Urinary Excretion of Aldosterone Test:
In the 24-hour urinary excretion of aldosterone test, a patient eats a high-salt diet for 5 days before measuring the amount of aldosterone in the urine over a 24-hour period. In patients with primary hyperaldosteronism, aldosterone will not be suppressed by the salt load, and the level of aldosterone in the urine will be high.

Saline Suppression Test:
In the saline suppression test, the patient is given a salt solution through an IV, after which the levels of aldosterone and renin in the blood are measured. In patients with primary hyperaldosteronism, the level of aldosterone in the blood is still high and the level of renin is low even after this salt loading.

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