A 24-hour urinary aldosterone excretion rate test measures the level of aldosterone that passes through your urine in a 24-hour period. It is an indirect measurement of the level of aldosterone in your blood.
Aldosterone is a steroid hormone excreted from the adrenal glands. It tells the kidneys to maintain the balance of salt, water, and potassium in your body. Aldosterone is secreted by the adrenal glands to aid in the control of your blood pressure.
Salt is an important mineral and electrolyte your body needs. You may recognize the term “electrolytes” from sports drink commercials. Salt helps retain water in the body, and it aids in the healthy functioning of nerves and muscles.
The test is non-invasive and painless.
Why a 24-Hour Urinary Aldosterone Excretion Rate Test Is Performed
The 24-hour urinary aldosterone excretion rate test is performed to test the levels of aldosterone in the blood. Your doctor may order the test to check for various conditions related to aldosterone production.
One study published in Hypertension: Journal of the American Heart Association found that there is a strong association between an enlarged heart muscle and the excretion of sodium and aldosterone in the urine. The 24-hour urinary test helps determine the relationship between sodium excretion and aldosterone levels.
A 24-hour urinary aldosterone excretion rate test may also be used to help determine if you have one of the following conditions, or to rule out high aldosterone secretion as a cause of another condition.
Conditions related to high aldosterone secretion include:
- Bilateral adrenal hyperplasia: the adrenal glands—two glands attached to the tops of the kidneys—grow and enlarge abnormally.
- Cirrhosis: this is known as the “alcoholic’s death,” as it is most often caused by excessive drinking. It scars and hardens the liver.
- Conn’s syndrome: caused by excess aldosterone in the blood, typically the only symptom of this condition is high blood pressure.
- Diuretics abuse: diuretics, more often known as “water pills,” are used to treat several conditions, such as high blood pressure. They can be abused as a form of weight control.
- Laxative abuse: laxatives, used to help soften stools associated with constipation, can be abused as a form of weight loss.
Abusing diuretics and laxatives could also be a sign of an eating disorder or body dysmorphic disorder, a type of mental illness in which a person obsesses about a perceived flaw in his or her appearance. Both conditions require help from a mental health professional.
How a 24-Hour Urinary Aldosterone Excretion Rate Test is Performed
The test carries no risks and is relatively easy to perform. It does, however, involve urinating into a container that your doctor will provide, so you may want to pick a 24-hour period during which you can stay at home.
For Infants and Young Children
Your doctor will often provide special collection bags for infants and children still in diapers. These bags will typically be long plastic sacs with an adhesive ring on one end.
Clean your child’s urethra—the opening where urine is expelled—before applying the bag. Remove the cover from the adhesive and apply the bag over the infant’s genitals. For boys, insert the penis into the hole of the bag. For the girls, ensure that the hole covers the labia.
This may require a few separate tries, as infants may shake the adhesive loose and spill urine. Regularly checking the bag could help improve the chances of proper collection.
The first day, your first urination should be done into your toilet and flushed. (Gentlemen, make sure to leave the seat down afterward.) After this first urination, all other urine for the day should be done into your container.
Your first urination should be done into the container the following morning. Store the sample in your refrigerator once you securely cap the container. Make sure to label it correctly with your name and contact information as your doctor’s office advises.
Follow any other instructions your doctor provides.
How to Prepare for a 24-Hour Urinary Aldosterone Excretion Rate Test
Depending on the condition your doctor may suspect, he or she may have specific instructions for you to follow during your collection. Here are a few general rules to follow:
- Consume less than 3 grams of sodium per day up to 2 weeks before the collection begins.
- Stop taking any medications your doctor advises. Those medications that could affect aldosterone levels include lithium, ACE inhibitors, and non-steroidal anti-inflammatory drugs (NSAIDs).
- Avoid caffeine, such as coffee, tea, sodas, chocolates, or energy drinks.
- Make sure to drink enough water to produce a sufficient sample size.
After a 24-Hour Urinary Aldosterone Excretion Rate Test
Schedule a follow-up appointment with your doctor to discuss your laboratory results. Your doctor will explain your aldosterone levels, as well as the significance of the results for your long-term health.