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Aldosterone and Renin

Formal name: Aldosterone and Renin
Related tests: Cortisol, Electrolytes, Potassium
The Test
 
How is it used?
When is it ordered?
What does the test result mean?
Is there anything else I should know?

How is it used?
Although some doctors measure either plasma or urine aldosterone by itself, in most cases it is necessary to measure both renin and aldosterone (and occasionally cortisol) to get a complete picture of what is happening with hormone production. These tests may be ordered to help diagnose and to monitor conditions associated with aldosterone excess or deficiency. The table below indicates the changes in renin, aldosterone, and cortisol that occur with different disorders. 
 

Disorder

Aldosterone

Cortisol

Renin

Primary hyperaldosteronism (Conn’s syndrome)

High

Normal

Low

Secondary hyperaldosteronism

High

Normal

High

Cushing’s syndrome

Low-normal

High

Low

Adrenal insufficiency (Addison's disease)

Low

Low

High

Pituitary disease

Normal

Low

Normal


Primary hyperaldosteronism is caused by the overproduction of aldosterone by the adrenal glands, usually by a benign tumor of one of the glands. The high aldosterone level increases reabsorption of sodium (salt) and loss of potassium by the kidneys, resulting in an electrolyte imbalance. Primary hyperaldosteronism is sometimes called Conn's syndrome. Symptoms are not typically present, although muscle weakness can occur if potassium levels are very low. The presence of hypokalemia in a person with hypertension suggests the need to look for hyperaldosteronism.

Secondary hyperaldosteronism, which is more common, can occur as a result of anything that decreases blood flow to the kidneys, decreases blood pressure, or lowers sodium levels. The most important cause is narrowing of the blood vessels that supply the kidney, termed renal artery stenosis. This causes high blood pressure due to high renin and aldosterone, that may be cured by surgery or angioplasty. Sometimes, to see if only one kidney is affected, a catheter is inserted through the groin and blood is collected directly from the veins draining the kidney (renal vein renin levels); if the value is significantly higher in one side, this indicates where the narrowing of the artery is present. Similarly, blood may sometimes be taken from both of the adrenal veins to determine whether there is a difference in the amount of aldosterone (and sometimes cortisol) produced by each of the adrenal glands. Secondary hyperaldosteronism may also be seen with congestive heart failure, cirrhosis, kidney disease, and toxemia of pregnancy.

Hypoaldosteronism (decreased production) usually occurs as part of adrenal insufficiency; it causes dehydration, low blood pressure, hyperkalemia, and hyponatremia.



When is it ordered?
A plasma and/or 24-hour urine aldosterone and a plasma renin may be ordered when a patient has high blood pressure and a low potassium. Aldosterone levels are sometimes ordered, along with other tests, when a doctor suspects that a patient has adrenal insufficiency. Since primary aldosteronism is a potentially curable cause of hypertension, and because it is often resistant to conventional treatment for high blood pressure, some doctors order aldosterone and renin levels when they want to help clarify the treatments that are likely to be effective in patients with high blood pressure.



What does the test result mean?
NOTE: This test has no single number that identifies an abnormal result. Your lab report (see a sample report) should include a range of numbers (reference range) that identifies what is expected for you based on your age, sex, and the method used in that laboratory. You can find more information about expected results at Reference Ranges and What They Mean. Lab Tests Online strongly recommends that you discuss the meaning of your test results with your doctor.

The changes in plasma aldosterone, cortisol, and renin are summarized in the table earlier on the page. High levels of serum and urine aldosterone, along with a low plasma renin, indicate primary aldosteronism. Secondary aldosteronism, on the other hand, is characterized by an increase in both aldosterone and renin.

A low aldosterone is usually part of adrenal insufficiency or Addison's disease. In infants with congenital adrenal hyperplasia, the infant lacks an enzyme needed to make cortisol; in some cases, this also decreases production of aldosterone. This is a rare cause of low aldosterone.


Is there anything else I should know?
The amount of salt in the diet and medications, such as over-the-counter pain relievers of the non-steroid class (such as Motrin and Advil), diuretics (water pills), beta blockers, steroids, angiotensin-converting enzyme (ACE) inhibitors, and oral contraceptives can affect the test results. Many of these drugs are used to treat high blood pressure. Your doctor will tell you if you should change the amount of sodium (salt) you ingest in your diet, your use of diuretics or other medications, or your exercise routine for aldosterone testing.

Aldosterone levels fall to very low levels with severe illness, so testing should not be done at times when a person is very ill. Stress and strenuous exercise can temporarily increase aldosterone results.






This article was last reviewed on April 3, 2006.
This page was last modified on April 8, 2009.
The review date indicates when the article was last reviewed from beginning to end to ensure that it reflects the most current science. A review may not require any modifications to the article, so the two dates may not always agree.
The modified date indicates that one or more changes were made to the page. Such changes may or may not result from a full review of the page, so the two dates may not always agree.
 
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