Test Overview

An aldosterone test measures the level of aldosterone (a hormone made by the adrenal glands) in the urine. Aldosterone helps regulate sodium and potassium levels in the body. This helps control blood pressure and the balance of fluids and electrolytes in the blood.

The kidney hormone renin normally stimulates the adrenal glands to release aldosterone. High levels of both renin and aldosterone are normally present when the body is trying to conserve fluid and salt (sodium). When a tumour that makes aldosterone is present, your aldosterone level will be high while a renin level will be low. Usually a renin activity test is done when the aldosterone level is measured.

Why It Is Done

An aldosterone test is done to:

• Measure the amount of aldosterone released into the body by the adrenal glands.
• Check for a tumour in the adrenal glands.
• Find the cause of high blood pressure or low potassium levels. This is done when overactive adrenal glands or an abnormal adrenal growth are suspected.

How To Prepare

Eat foods with a normal amount of sodium (2,300 mg per day) for at least 2 weeks before the test. Do not eat foods that are very salty, such as bacon, canned soups and vegetables, olives, bouillon, soy sauce, and salty snacks like potato chips or pretzels. A low-salt diet can also increase aldosterone levels. Tell your doctor if you are on a low-salt food plan.

Do not eat natural black licorice for at least 2 weeks before an aldosterone test.

You may be asked to stop taking some medicines for about 2 weeks before the test. These include hormones (such as progesterone and estrogen), corticosteroids, diuretics, and many medicines used to treat high blood pressure, especially spironolactone (Aldactone) and eplerenone (Inspra).

How It Is Done

This test is usually done at home. You must collect all the urine you produce in a 24-hour period.

• When you first get up in the morning, urinate into the toilet. Don't save this urine. This marks the start of your 24-hour period.
• For the next 24 hours, collect all your urine. Your doctor or lab will give you a large container to store it in. Urinate into a separate small, clean container. Then pour the urine into the large container. Don't touch the inside of the containers with your fingers.
• Keep the large container in the refrigerator.
• Empty your bladder for the last time at or just before the end of the 24-hour period. Add this urine to the large container, and write down the time.
• Do not get toilet paper, pubic hair, stool (feces), menstrual blood, or anything else in your urine sample.

How It Feels

This test usually doesn't cause any pain or discomfort.

Risks

There are no known risks from having this test.

Results

Normal

Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.

High values

High aldosterone levels can be caused by:

• A tumour in the adrenal glands (Conn's syndrome).
• Heart failure.
• Kidney disease.
• Liver disease.
• A condition during pregnancy that causes high blood pressure (pre-eclampsia).
• Some medicines that are used to treat high blood pressure.

Low values

Low aldosterone levels can be caused by:

• Addison's disease.
• Kidney disease, such as the types of kidney disease seen in people who also have diabetes.
• Heparin treatment. Heparin is a medicine that helps prevent blood clots. It is given as a shot.