What are the other Names for this Test? (Equivalent Terms)
- Plasma Renin Activity Test
- PRA Test
- Urine Aldosterone Test
What is the Aldosterone and Renin Test? (Background Information)
- Aldosterone is a hormone that is produced by the adrenal glands (glands present on top of the kidneys, one on each side)
- Renin is an enzyme produced by the kidneys, which stimulate the adrenal glands to produce aldosterone. It is produced in the kidney, whenever there is a fall in the blood pressure, or when the sodium level in the blood, flowing through the kidney, is lower than normal
- Renin, through a series of reactions involving other enzymes, increases aldosterone production by the adrenal glands. One of the substances produced in this pathway, angiotensin II, constricts the blood vessels (makes the blood channels narrower), thereby raising blood pressure, while the aldosterone helps the kidneys in reabsorbing sodium and eliminating potassium from the body
- The Aldosterone and Renin Test can be used to detect any excesses or deficiencies in their amounts. Testing for aldosterone may be done on a sample of blood or a 24-hour urine sample, while renin levels are measured in blood
What are the Clinical Indications for performing the Aldosterone and Renin Test?
Indications for Aldosterone and Renin Testing include:
- Symptoms of aldosterone excess (hyperaldosteronism), due to possibly high levels of sodium and low levels of potassium in blood, such as:
- High blood pressure
- Muscle weakness
- Symptoms of aldosterone deficiency, such as low blood pressure, with low blood sodium, high blood potassium levels. Aldosterone deficiency occurs as part of a condition, called adrenal insufficiency. Other symptoms of this condition may include:
- Low blood glucose
- Belly aches
- Joint pain
- Dark skin patches
How is the Specimen Collected for Aldosterone and Renin Test?
- Blood - for aldosterone and renin
- Urine - for aldosterone
- Blood sample is drawn through a needle inserted into the vein (arm)
- Sometimes, a blood sample may be drawn by a radiologist, via a catheter introduced into any of the following:
- Adrenal vein (vein coming out of adrenal gland), to measure the amount of aldosterone
- Renal vein (vein coming out of the kidney), to measure the amount of renin
- A 24-hour urine sample is collected at home, in a clean, sterile container over a 24-hour period, with refrigeration of the sample, in between collections
- Medications, such as NSAID pain relievers (like ibuprofen), steroids, diuretics, beta blockers, angiotensin converting enzyme inhibitors, oral contraceptives, and dietary salt, can influence the test results. Normally, the physician will provide specific advice to each individuals on the usage of these medications and the amount of dietary salt permissible, prior to testing
- Caffeinated beverages may affect the 24-hour urine sample test and may have to be avoided, prior to testing
- Avoid hard liquorice (or licorice, a kind of root) for 2 weeks, prior to testing
- It will be necessary to either sit upright or lie down for a period of 15-30 minutes, prior to blood sample collection
What is the Significance of the Aldosterone and Renin Test Result?
The significance of the possible test outcomes is as follows:
- High aldosterone and low renin:
- Occurs in a condition called primary aldosteronism
- Due to overproduction of aldosterone, by one or both the adrenal glands - may occur due to an adrenal tumor
- Measuring aldosterone levels from adrenal veins, located on each side separately, can help localize the gland that is diseased/functioning abnormally
- High aldosterone and high renin:
- Occurs in a condition called secondary aldosteronism
- May occur in many conditions, such as heart failure, renal artery stenosis (arterial blood vessel to the kidney is narrowed), liver cirrhosis (scarring of the liver), dehydration, etc.
- In all these disease states, the blood flow to the kidney is less, which prompts the kidney to produce more renin, leading to increased levels of renin and aldosterone in blood
- Measuring renin levels from the renal veins, located on each side, can help identify the site of arterial narrowing, if renal artery stenosis is the cause
- Low aldosterone and high renin: This occurs in a condition called adrenal insufficiency, or Addison disease. In this disease, the blood level of cortisol is also lowered
- Low aldosterone and low renin: This may occur along with high blood levels of cortisol in a condition, called Cushing’s syndrome
The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.
Additional and Relevant Useful Information:
- Aldosterone level in blood can vary through the day and with changes in body position. Hence, some physicians prefer testing aldosterone in a 24-hour urine sample
- Severe illness, exercise, stress, and pregnancy, can influence the test results
Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.