Catecholamines tests – Description – Definition – Purpose – Risks
Definition
Catecholamines is a collective term for the hormones epinephrine, norepinephrine, and dopamine.
Manufactured chiefly by the chromaffin cells of the adrenal glands, these hormones are involved in readying the body for the ‘‘fight-or-flight’’ response (also known as the alarm reaction). When these hormones are released, the heart beats stronger and faster, blood pressure rises, more blood flows to the brain andmuscles, the liver releases stores of energy as a sugar the body can readily use (glucose), the rate of breathing increases and airways widen, and digestive activity slows. These reactions direct more oxygen and fuel to the organs most active in responding to stress–mainly the brain, heart, and skeletal muscles.
Description
The catecholamines test can be performed on either blood or urine. If performed on blood, the test may require one or two samples, depending on the physician’s request. The first blood sample will be drawn after the patient has been lying down in a warm, comfortable environment for at least 30 minutes.
If a second sample is needed, the patient will be asked to stand for 10 minutes before the blood is drawn. Instead of a venipuncture, which can be stressful for the patient, possibly increasing catecholamine levels in the blood, a plastic or rubber tube-like device called a catheter may be used to collect the blood samples.
The catheter would be inserted in a vein 24 hours in advance, eliminating the need for needle punctures at the time of the test. It may take up to a week for a lab to complete testing of the samples. Because blood levels of catecholamines commonly go up and down in response to such factors as temperature, stress, postural change, diet, smoking, obesity, and many drugs, abnormally high blood test results should be confirmed with a 24-hour urine test. In addition, catecholamine secretion from a tumor may not be steady, but may occur periodically during the day, and potentially could be missed when blood testing is used. The urine test provides the laboratory with a specimen that reflects catecholamine production over an entire 24-hour period. If urine is tested, the patient or a healthcare worker must collect all the urine passed over the 24-hour period.
Purpose
Pheochromocytoma (a tumor of the chromaffin cells of the adrenal gland) and tumors of the nervous system (neuroblastomas, ganglioneuroblastomas, and ganglioneuromas) that affect hormone production can cause excessive levels of different catecholamines to be secreted. This results in constant or intermittent high blood pressure (hypertension). Episodes of high blood pressure may be accompanied by symptoms such as headache, sweating, palpitations, and anxiety. The catecholamines test can be ordered, then, to determine if high blood pressure and other symptoms are related to improper hormone secretion and to identify the type of tumor causing elevated catecholamine levels.
Preparation
It is important that the patient refrain from using certain medications, especially cold or allergy remedies, for two weeks before the test. Certain foods—including bananas, avocados, cheese, coffee, tea, cocoa, beer, licorice, citrus fruit, vanilla, and Chianti—must be avoided for 48 hours prior to testing. However, people should be sure to get adequate amounts of vitamin C before the test, because this vitamin is necessary for catecholamine formation. The patient should be fasting (nothing to eat or drink) for 10 to 24 hours before the blood test and should not smoke for 24 hours beforehand. Some laboratories may call for additional restrictions. As much as possible, the patient should try to avoid excessive physical exercise and emotional stress before the test, because either may alter test results by causing increased secretion of epinephrine and norepinephrine.
Patients collecting their own 24-hour urine samples will be given a container with special instructions. The urine samples must be refrigerated.
Risks
Risks for the blood test are minimal, but may include slight bleeding from the venipuncture site, fainting or feeling lightheaded after blood is drawn, or blood accumulating under the puncture site (hematoma). There are no risks for the urine test.
How the Test is Performed
For this test, you must urinate into a special bag or container every time you use the bathroom for 24-hour period.
* On day 1, urinate over the toilet into the container or bag when you wake up in the morning. Close the container tightly. Keep it in the refrigerator or a cool place during the collection period.
* Urinate into the special container every time you use the bathroom for the next 24 hours.
* On day 2, urinate into the container in the morning again when you wake up.
* Label the container with your name, the date, the time of completion, and return it as instructed.
For an infant:
Thoroughly wash the area around the urethra (the hole where urine flows out). Open a urine collection bag (a plastic bag with an adhesive paper on one end).
* For males, place the entire penis in the bag and attach the adhesive to the skin.
* For females, place the bag over the two folds of skin on either side of the vagina (labia). Put a diaper on the baby (over the bag).
Check the infant frequently, and change the bag after the infant has urinated. Empty the urine from the bag into the container provided by your doctor.
Because lively infants can cause the bag to move, this procedure may take a couple of attempts. You may need extra collection bags.
When finished, label the container and return it as instructed.
How to Prepare for the Test
Acute stress and vigorous exercise may affect the test results.
Foods that can increase urinary catecholamines include coffee, tea, bananas, chocolate, cocoa, citrus fruits, and vanilla. Avoid these foods for several days prior to the test.
Certain drugs can also affect test results. Your health care provider may tell you to stop taking certain medicines before the test. Never stop taking medicine without first talking to your doctor.
The following drugs can increase catecholamine measurements:
* Acetaminophen (Tylenol)
* Aminophylline
* Caffeine
* Chloral hydrate
* Clonidine
* Disulfiram
* Erythromycin
* Insulin
* Levodopa
* Lithium
* Methenamine
* Methyldopa
* Nicotinic acid (large doses)
* Nitroglycerin
* Quinidine
* Tetracyclines
Drugs that can decrease catecholamine measurements include:
* Clonidine
* Disulfiram
* Guanethidine
* Imipramine
* MAO inhibitors
* Phenothiazines
* Reserpine
* Salicylates
How the Test Will Feel
The test involves only normal urination, and there is no discomfort.
Why the Test is Performed.
The test is usually done to diagnose an adrenal gland tumor called pheochromocytoma. It may also be used to diagnose neuroblastoma. Urine catecholamine levels are increased in most persons with neuroblastoma.
The urine test for catecholamines may also be used to monitor those who are receiving treatment for these conditions.
Normal Results.
All of the catecholamines are broken down into inactive substances that appear in the urine:
* Dopamine becomes Homovanillic acid (HVA)
* Norepinephrine becomes normetanephrine and vanillylmandelic acid (VMA)
* Epinephrine becomes metanephrine and VMA
The following normal values represent the amount of the substance found in the urine over a 24 hour period. Normal values vary from lab to lab, but in general are as follows:
* Dopamine: 65 – 400 micrograms (mcg)/24 hours.
* Epinephrine: 0.5 – 20 mcg/24 hours.
* Metanephrine: 24 – 96 mcg/24 hours (some laboratories give the range as 140 – 785 mcg/24-hours)
* Norepinephrine: 15 – 80 mcg/24 hours
* Normetanephrine: 75 – 375 mcg/24 hours
* Total urine catecholamines: 14 – 110 mcg/24 hours
* VMA: 2 – 7 milligrams (mg)/24 hours
What Abnormal Results Mean
Elevated levels of urinary catecholamines may indicate:
* Acute anxiety
* Ganglioblastoma (very rare)
* Ganglioneuroma (very rare)
* Neuroblastoma (rare)
* Pheochromocytoma (rare)
* Severe stress
Additional conditions under which the test may be performed:
* Multiple endocrine neoplasia (MEN) II
Risks
There are no risks.
Considerations
Several foods and drugs, as well as physical activity and stress, can affect the accuracy of this test.
Resources
Books
Pagana, Kathleen Deska. Mosby's Manual of Diagnostic and Laboratory Tests. St. Louis: Mosby, Inc., 1998.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.
http://adam.about.com
Young WF. Adrenal medulla, catecholamines, and pheochromocytoma. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 246.
