Blood-tests Explained


Disclaimer:

This website is intended to assist with patient education and should not be used as a diagnostic, treatment or prescription service, forum or platform. Always consult your own healthcare practitioner for a more personalised and detailed opinion

Aldosterone


At a Glance

Why Get Tested?

To determine if your aldosterone and renin levels are abnormal, to help diagnose a hormonal (endocrine) disorder such as primary aldosteronism (PA, Conn syndrome)

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

Sample Required?

A blood sample drawn from a vein in your arm or a 24-hour urine sample; sometimes at specialized medical centers, blood from the kidney (renal) or adrenal veins is also collected.

Test Preparation Needed?

For a blood aldosterone and renin measurement, the healthcare practitioner 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.

Thumbnail diagram of the adrenal gland

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 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, 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 drawn by needle from a vein in the arm to measure blood aldosterone and/or renin. Some healthcare practitioners 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 at major medical centers by a specially trained radiologist.

Is any test preparation needed to ensure the quality of the sample?

For a blood aldosterone and renin measurement, the healthcare practitioner 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?")

The Test