Aldosterone

Definition

An aldosterone test measures the amount of aldosterone in serum (blood).

Why the Aldosterone is Performed

This test is performed to investigate hard-to-control blood pressure, orthostatic hypotension (low blood pressure upon standing), and certain fluid and electrolyte disorders.

Aldosterone is a hormone released by the adrenal glands. It is part of the complex mechanism used by the body to regulate blood pressure. Aldosterone is the main sodium-retaining hormone from the adrenal gland. It increases the reabsorption of sodium and water along with the excretion of potassium in the distal tubules of the kidneys. This action raises blood pressure.

Frequently, blood aldosterone levels are combined with other blood tests (plasma renin activity) or provocative tests (captopril test, intravenous saline infusion test or ACTH infusion test) in order to diagnosis over- or under-production of the hormone.

How the Aldosterone is Performed

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and cause the vein to swell with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

For infants or young children, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any bleeding.

How to Prepare for the Aldosterone

Your doctor may provide instructions on dietary or supplemental salt intake prior to testing.

How the Aldosterone 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.

Risks

• Excessive bleeding
• Fainting or feeling lightheaded
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)
• Multiple punctures to locate veins

Considerations

Factors that can affect aldosterone measurements include strenuous exercise, acute stress, and dietary salt intake.

Many medications can influence aldosterone levels, including diuretics, lithium, calcium channel blockers, ACE inhibitors, propranolol, NSAIDs, and heparin.

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.

Normal Results

Lying down: 2 to 16 ng/dl

Upright: 5 to 41 ng/dl

Normal value ranges may vary slightly among different laboratories.

Note: ng/dl = nanograms per deciliter

What Abnormal Results Mean

Higher-than-normal levels of aldosterone may indicate:

• Primary hyperaldosteronism (rare)
• Bartter syndrome (extremely rare)
• Secondary hyperaldosteronism from cardiac or kidney disease
• Cushing's syndrome (rare)
• Very low sodium diet

Lower-than-normal levels of aldosterone may indicate:

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

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