At a Glance
Why Get Tested?
When to Get Tested?
When you develop symptoms or signs associated with increased aldosterone production, such as elevated blood pressure, muscle weakness, and low potassium, or low aldosterone production, such as low blood pressure, high potassium, and low sodium
A blood sample drawn from a vein in your arm or a 24-hour urine sample; sometimes blood from the kidney (renal) or adrenal veins is also collected.
Test Preparation Needed?
For a blood aldosterone and renin measurement, your doctor may ask you to be upright or lying down (e.g., for 15-30 minutes) prior to drawing blood. You may also be instructed to avoid certain foods, beverages, or medications before the test. Follow any instructions you are given.
The Test Sample
What is being tested?
Aldosterone is a hormone that plays an important role in maintaining normal sodium and potassium concentrations in blood and in controlling blood volume and blood pressure. Renin is an enzyme that controls aldosterone production. These tests measure the levels of aldosterone and renin in the blood and/or the level of aldosterone in urine.
Aldosterone is produced by the adrenal glands located at the top of each kidney, in their outer portion (called the adrenal cortex). Aldosterone stimulates the retention of sodium (salt) and the excretion of potassium by the kidneys. Renin is produced by the kidneys and controls the activation of the hormone angiotensin, which stimulates the adrenal glands to produce aldosterone.
The kidneys release renin when there is a drop in blood pressure or a decrease in sodium chloride concentration in the tubules in the kidney. Renin cleaves the blood protein angiotensinogen to form angiotensin I, which is then converted by a second enzyme to angiotensin II. Angiotensin II causes blood vessels to constrict, and it stimulates aldosterone production. Overall, this raises blood pressure and keeps sodium and potassium at normal levels.
A variety of conditions can lead to aldosterone overproduction (hyperaldosteronism, usually just called aldosteronism) or underproduction (hypoaldosteronism). Since renin and aldosterone are so closely related, both substances are often tested together to identify the cause of an abnormal aldosterone.
How is the sample collected for testing?
A blood sample is taken by needle from a vein in the arm to measure blood aldosterone and/or renin. Some doctors prefer 24-hour urine collection for aldosterone since blood aldosterone levels vary throughout the day and are affected by position. In some cases, blood is collected from the renal (for renin) or adrenal (for aldosterone) veins by insertion of a catheter; this is done in the hospital by a radiologist.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
For a blood aldosterone and renin measurement, the doctor may ask you to be upright or lying down for a period of time (e.g., 15-30 minutes) prior to sample collection. You may also be instructed to avoid certain beverages, foods, or medications before the test. Follow any instructions you are given. (For more, see the section "Is there anything else I should know?")
Ask a Laboratory Scientist
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Sources Used in Current Review
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The American Association of Endocrine Surgeones. Primary hyperaldosteronism. Available online at http://endocrinediseases.org/adrenal/hyperaldosteronism.shtml through http://endocrinediseases.org. Accessed on Jan. 4, 2013.
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(Reviewed August 2012 by Ashley B. Grossman.) Secondary Aldosteronism. The Merck Manual. Available online through http://www.merckmanuals.com. Accessed Jan. 8, 2013.
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(Updated August 2012.) Primary Aldosteronism Workup. Medscape. Available online at http://emedicine.medscape.com/article/127080-workup#aw2aab6b5b9 through http://emedicine.medscape.com. Accessed Jan. 28, 2012.
Bartter syndrome. MedlinePlus Medical Encyclopedia. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000308.htm. Accessed February 2014.
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Bartter's Syndrome. National Organization for Rare Disorders. Available online at http://www.rarediseases.org/rare-disease-information/rare-diseases/byID/589/viewAbstract through http://www.rarediseases.org. Accessed February 2014.
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