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Aldosterone is a corticosteroid secreted by the adrenal gland. This hormone regulates water balance and salts (potassium and sodium). This hormone helps to also balance electrolytes and control blood pressure.
The aldosterone suppression test is ultimately done to measure a patient's aldosterone levels in the blood. This blood test is often done in combination with the renin test. Renin, a kidney hormone, is responsible for stimulating the adrenal glands so that they release aldosterone. When both aldosterone and renin levels are high, it typically indicates that the body is trying to conserve sodium and fluid.
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Why is this Blood Test Done?
An aldosterone suppression test is performed to:
- Measure how much aldosterone the adrenal glands are releasing into the body.
- To look for adrenal gland tumors.
- To look for the cause of low blood potassium levels or high blood pressure. This is performed when an abnormal adrenal growth or overactive adrenal glands are suspected.
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How to Prepare for this Blood Test
This test is often performed during routine blood testing and no preparation is necessary for routine blood testing. However, if any follow-up aldosterone blood testing is necessary, the doctor may provide special instructions, including:
- Eating a normal amount of sodium per day for two weeks. 2,300 milligrams is a normal amount of sodium. Patients should avoid high sodium foods and low sodium foods and strive to take in as close to 2,300 milligrams a day as possible.
- Black licorice should not be consumed for two weeks prior to this test.
A variety of medications may alter the test results so it is important the doctor knows about all of the patients medications, both prescription and non-prescription. Some medications may have to be stopped two weeks prior to the test. These include:
- Hormones (such as estrogens and progesterone)
- High blood pressure medications (especially eplerenone, spironolactone, and beta-blockers)
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How is this Blood Test Done?
The test will begin by wrapping a tourniquet around the patient's upper arm to help enlarge the veins by stopping the flow of blood. The site site in which the needle will be inserted will be cleaned with alcohol. The needle will then be inserted into the vein and a tube will be connected to the vacutainer to collect the blood. Once it is filled, the tourniquet will be removed. A cotton ball is placed over the puncture site and the needle is removed. Pressure will be applied to the site and a bandage will be placed over the puncture.
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What are the Risks Involved with this Blood Test?
The risks are minimal for most people. The possible risks include:
- A small bruise at the puncture site.
- Vein swelling, also referred to as phlebitis.
- Ongoing bleeding in patients with pre-exising bleeding disorders or those taking blood-thinning medications (such as warfarin or aspirin). Patients taking blood-thinning medications and those with clotting or bleeding problems should tell their doctor about these prior to having this blood test done.
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What to the Results Mean?
The results of the aldosterone suppression test can indicate a number of things. If aldosterone levels are high, but renin is low, the patient may have primary hyperaldosteronism. If both aldosterone and renin levels are high, the patient may have secondary hyperaldosteronism.
High levels of this hormone may indicate:
- Adrenal gland tumor
- Liver disease
- Kidney disease
- Heart failure
When levels of aldosterone are high, patients can experience high blood pressure, weakness, low blood-potassium levels, muscle cramps, and hand tingling and numbness.
Low levels of this hormone may indicate:
- Addison's disease
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What Can Affect the Test?
There are certain things that can affect this test and its results. These include:
- Consuming a large amount of natural black licorice
- Being of a younger age
- Being pregnant, specifically in the third trimester
- Being emotionally stressed
- Taking certain medications, such as female hormones, heparin, laxatives, diuretics, corticosteroids, opiates, or non-steroidal anti-inflammatory drugs. Medications taken to treat high blood pressure can also alter the results.
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WebMD. (2008). Aldosterone in Blood. Retrieved on June 22, 2010 from WebMD: http://www.webmd.com/a-to-z-guides/aldosterone
Lab Tests Online. (2009). Aldosterone and Renin. Retrieved on June 22, 2010 from Lab Tests Online: http://www.labtestsonline.org/understanding/analytes/aldosterone/glance.html
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Phlebotomy Tray: Bubbels – sxc.hu