Plasma Renin Activity (PRA)

Renin also acts as a hormone (a chemical messenger in your bloodstream that controls the actions of certain cells or organs) to help control your blood pressure. Renin controls the production of another hormone called aldosterone, which is made in your adrenal glands. These are two small glands located above the kidneys. Aldosterone helps keep your blood pressure stable. It does this by helping to balance the levels of two electrolytes in your blood: potassium and sodium.

Usually, if renin increases or decreases, aldosterone does the same. These levels are highest in the morning and change throughout your day. Your position (sitting, standing, etc.), stress level, and certain medicines can affect your renin and aldosterone levels. If your renin and/or aldosterone levels are not normal, it can be a sign of an adrenal gland disorder. Because the two hormones work together, an aldosterone test is often done at the same time as a renin test.

You may need a renin test if you've been diagnosed with high blood pressure, especially if it doesn't respond well to standard blood pressure medicines. The test can show whether primary aldosteronism is causing the condition. Sometimes, primary aldosteronism causes low potassium levels, so you may also need this test if you have symptoms of low potassium.

If your results show a higher-than-normal amount of renin, it may be a sign of: Addison disease (also called adrenal insufficiency), a condition in which your adrenal glands don't make enough of certain hormones; cirrhosis, scarring of the liver; or dehydration.

If your results show a lower-than-normal amount of renin, it may be a sign of primary aldosteronism (PA) or kidney disease.

Most often, your renin test results will be compared with your aldosterone test results. Lower than normal renin / lower than normal aldosterone may mean you have Cushing's syndrome, a disorder in which the adrenal glands make too much cortisol. Lower than normal renin / higher than normal aldosterone may mean you have PA. Higher than normal renin / lower than normal aldosterone may mean you have Addison disease. Higher than normal renin / higher than normal aldosterone may mean you have secondary aldosteronism — your adrenal glands are healthy, but another medical condition (such as diseases of the heart, liver, or kidneys) is causing them to make too much aldosterone.

Providers often look at the ratio of aldosterone to renin (sometimes called the ARR). A high ratio along with a clearly elevated aldosterone level is a screening sign for primary aldosteronism and usually leads to more testing.

Depending on your results, your provider may recommend medicines and/or diet and lifestyle changes to treat your condition. If you have questions about your results, talk to your provider.