Aldosterone

Definition

An aldosterone test measures the amount of the hormone aldosterone in blood.

How the test is performed

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

How to prepare for the test

Your doctor may instruct you about your salt intake before the test.

How the test will feel

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed

This test is performed to investigate:

• Certain fluid and electrolyte disorders
• Hard to control blood pressure
• Low blood pressure upon standing (orthostatic hypotension)

Aldosterone is a hormone released by the adrenal glands. It helps the body regulate blood pressure.

Aldosterone increases the reabsorption of sodium and water and the release of potassium in the kidneys. This action raises blood pressure.

Often, blood aldosterone levels are combined with other tests to diagnose over- or under-production of the hormone. These tests may include:

• ACTH infusion test
• Captopril test
• Intravenous saline infusion test
• Plasma renin activity

Normal Values

Lying down: 2 to 16 ng/dL

Upright: 5 to 41 ng/dL

Note: ng/dL = nanograms per deciliter

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What abnormal results mean

Higher than normal levels of aldosterone may indicate:

• Bartter syndrome (extremely rare)
• Primary hyperaldosteronism (rare)
• Secondary hyperaldosteronism from heart or kidney disease
• Very low-sodium diet

Lower than normal levels of aldosterone may indicate:

• Addison's disease (rare)
• Congenital adrenal hyperplasia
• Hyporeninemic hypoaldosteronism
• Very high-sodium diet

What the risks are

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

Special considerations

Factors that can affect aldosterone measurements include:

• Acute stress
• Dietary salt intake
• Strenuous exercise

Many medications can influence aldosterone levels, including:

• ACE inhibitors
• Calcium channel blockers
• Diuretics
• Heparin
• Lithium
• Nonsteroidal anti-inflammatory drugs (NSAIDs)
• Propranolol

References

Nieman LK. Adrenal cortex. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, PA: Saunders Elsevier; 2007: chap 245.