About the Test
Purpose of the test
Aldosterone and renin tests are used to evaluate whether the adrenal glands are producing appropriate amounts of aldosterone and to distinguish between the potential causes of excess or deficiency. The hormone may be measured in the blood or in a 24-hour urine sample, which measures the amount of aldosterone removed in the urine daily. Renin is always measured in blood.
These tests are most useful in testing for primary aldosteronism, also known as Conn’s syndrome, which causes high blood pressure. If the test is positive, aldosterone production may be further evaluated with stimulation and suppression testing.
Both aldosterone and renin levels are highest in the morning and vary throughout the day. They are affected by the body’s position, stress, and various prescribed medications.
What does the test measure?
Aldosterone is a hormone that plays an important role in maintaining normal sodium and potassium concentrations in the blood and in controlling blood volume and 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). The hormone stimulates the retention of sodium (salt) and the elimination 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. It is then converted by a second enzyme to angiotensin II, which causes blood vessels to constrict, and 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.
When should I get this test?
A blood aldosterone test and a renin test are usually ordered together when you have high blood pressure, especially if you also have low potassium. Even if potassium is normal, testing may be done if typical medications do not control high blood pressure or if hypertension develops early.
Primary aldosteronism is a potentially curable form of hypertension, so it is important to detect and treat it properly.
Aldosterone levels are occasionally ordered, along with other tests, when a health care practitioner suspects someone has adrenal insufficiency or Addison’s disease. One of those tests, the aldosterone stimulation test, also called ACTH stimulation, tests aldosterone and cortisol to determine if someone has Addison’s disease, low pituitary function, or a pituitary tumor.
A doctor may order a test when you develop symptoms or signs associated with increased aldosterone production, such as elevated blood pressure, muscle weakness, and low potassium. They may also order it for low aldosterone production, such as low blood pressure, high potassium, and low sodium.
Finding an Aldosterone and Renin Test
How can I get an aldosterone and renin test?
An aldosterone and renin test is typically ordered by your doctor if you have high blood pressure and low potassium or if you are showing certain symptoms. The test is usually taken at a doctor’s office, lab, or hospital.
Can I take the test at home?
Aldosterone and renin tests are not done at home.
How much does the test cost?
The cost of an aldosterone and renin test depends on your health insurance coverage and where you go for the test. You may be responsible for a copayment or deductible payment even if you are covered by insurance.
Taking an Aldosterone and Renin Test
An aldosterone and renin test is most commonly done by drawing blood from a vein in your arm. However, some health care practitioners prefer 24-hour urine collection for aldosterone since blood aldosterone levels vary throughout the day and are affected by position.
In some complex cases, blood is collected from the renal (for renin) or adrenal (for aldosterone) veins by inserting a catheter; this is done in the hospital at major medical centers by a specially trained radiologist.
Before the test
For a blood aldosterone and renin measurement, the health care practitioner may ask you to be upright or lying down for a period (e.g., 15 to 30 minutes) prior to sample collection. Before the test, you may also be instructed to avoid certain beverages, foods, or medications.
Your health care provider 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 before aldosterone testing.
Licorice may mimic aldosterone properties and should be avoided for at least two weeks before the test because it can decrease aldosterone results. Note that most soft licorice sold in North America does not actually contain licorice. Check the package label if you are uncertain, or bring a package to ask the health care practitioner.
During the test
A blood sample is drawn by needle from a vein in the arm to measure blood aldosterone and/or renin.
After the test
There shouldn’t be any aftereffects from taking an aldosterone and renin test. You may experience some slight bruising on your arm where the needle was inserted, but you can otherwise resume your normal activities.
Aldosterone and Renin Test Results
Receiving test results
Results for this test take anywhere from four to seven business days. Your health care provider or lab may contact you when results are available. Or, if you can access your records online, you could check to see if/when they are posted.
Interpreting test results
The table below indicates the changes in renin, aldosterone, and cortisol that occur with different disorders.
|Primary aldosteronism (Conn’s syndrome)||High||Normal||Low|
|Adrenal insufficiency (Addison’s disease)||Low||Low||High|
Primary aldosteronism (Conn’s syndrome) 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, often resulting in an electrolyte imbalance.
Signs and symptoms include high blood pressure, headache, and muscle weakness, especially if potassium levels are very low.
Lower than normal blood potassium (hypokalemia) in someone with hypertension suggests the need to look for aldosteronism. Sometimes, blood may be taken from both adrenal veins to determine whether only one or both adrenal glands are affected. Testing is done to determine whether there is a difference in the amount of aldosterone (and sometimes cortisol) produced by each of the adrenal glands.
Secondary aldosteronism, more common than primary aldosteronism, is caused by anything that leads to excess aldosterone, other than a disorder of the adrenal glands. It could be caused by any condition that decreases blood flow to the kidneys, decreases blood pressure, or lowers sodium levels.
Secondary aldosteronism may be seen with congestive heart failure, liver cirrhosis, kidney disease, and toxemia of pregnancy (pre-eclampsia). It is also common in dehydration. In these conditions, the cause of aldosteronism is usually obvious.
The most important cause of secondary aldosteronism is the narrowing of the blood vessels that supply the kidney, termed renal artery stenosis. This causes high blood pressure due to high renin and aldosterone and 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.
Hypoaldosteronism usually occurs as part of adrenal insufficiency. It causes dehydration, low blood pressure, a low blood sodium level, and a high potassium level. When infants lack an enzyme needed to make cortisol, a condition called congenital adrenal hyperplasia, this can decrease aldosterone production in some cases.
Whenever you get test results, ask your doctor to clarify anything you’re unsure about. Some questions to ask about an aldosterone and renin test include:
- What are some things that might impact my aldosterone and renin levels?
- Does an elevated amount of aldosterone mean I have Conn’s Syndrome?
- Could something else have caused the test results to be inaccurate?
- What follow-up tests should I get if my levels were not in the normal range?