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A blood test for catecholamines determines their level in the blood. The catecholamines include adrenaline, norepinephrine, and dopamine.
Adrenaline is the main hormone of the adrenal medulla, where it is formed by enzymatic synthesis from another hormone, norepinephrine, and accumulates in chromaffin cells.
Norepinephrine, in addition to being a hormone, is a neurotransmitter. Its synthesis occurs from dopamine predominantly in the postgangliar cells of the sympathetic nervous system, and less than 10% in the adrenal medulla, as well as in the central nervous system.
Dopamine is a CNS neurotransmitter that also acts as a mediator of local (paracrine) regulation in some organs, for example, in the mucosa of the gastrointestinal tract, kidneys. The source of dopamine is predominantly the nervous system. The share of formed in the gastrointestinal tract also accounts for a significant amount of dopamine circulating in the blood. In addition, part of dopamine is formed in the kidneys and excreted in the urine, but the adrenal glands make a minimal contribution to the total dopamine synthesis – less than 2%.
A doctor can give a direction for the study of catecholamines, suspecting the presence of pheochromocytoma. It is a tumor of the chromaffin cells of the adrenal medulla. Cells similar to these are found in other tissues, and islets of such cells function similarly to the adrenal medulla. With pheochromocytoma, the secretion of catecholamines increases many times over. Most pheochromocytomas are benign, but it is important to remove them so they do not interfere with normal adrenal function. Radical removal of the tumor leads to normalization of plasma catecholamine levels.
What is a catecholamine blood test?
The test measures the amount of the hormones adrenaline, norepinephrine, and dopamine in the blood. Catecholamines help the body respond to stress or fear and prepare it to respond appropriately in a similar situation. The adrenal glands release large amounts of catecholamines as a response to stress.
The duration of the work of catecholamines circulating in the blood is not very long, their half-life from circulation is minutes, while recapture by sympathetic nerve endings occurs and conversion into inactive forms under the action of enzymes. They are then metabolized in the liver and excreted by the kidneys in the urine.
Catecholamines increase heart rate, blood pressure, breathing rate, muscle strength, mental alertness, and the amount of blood flowing to major organs (brain, heart, and kidneys). They also reduce the amount of blood entering the skin and intestines.
Rare tumors such as pheochromocytoma can cause a sharp increase in catecholamines in the blood. This causes high blood pressure, excessive sweating, headaches, rapid heartbeat, tremors.
When to take a catecholamine test?
There are a number of symptoms for which you need to see a doctor. If the treating doctor already has specific suspicions of an illness, he may also refer the patient for a blood test. The main reasons to test the blood for catecholamines are:
- high blood pressure;
- fast, unusually heavy heartbeat;
- heavy sweating;
- severe headaches over a long period of time;
- pale skin, unexplained weight loss;
- feeling unusually frightened for no reason or feeling very anxious.
In addition, an indication for the determination of catecholamines and the ratio of their fractions may be a suspicion of a tumor of the nervous system: neuroblastoma, paraganglioma. Such a study helps to determine the localization and nature of catecholamine-secreting tumors.
How is the analysis done?
Blood sampling for this analysis must be done at the time of obvious clinical manifestations, for example, at the time of a hypertensive crisis.
The level of this hormone in some people may rise just because they are nervous about the upcoming test. Therefore, false-positive or false-negative test results cannot be ruled out. Therefore, you must always remain calm.
Pros and Cons of the procedure
The most important and main advantage of this study is that it can help confirm diseases. If they are detected in time, then there is a chance to quickly get rid of them. If you start the disease, the chances of recovery are significantly reduced.
The disadvantage of taking the test is that the procedure itself can cause stress, and this, in turn, will increase the level of catecholamines.
Be sure to warm up after the test (for example, drink warm tea) because the cold can increase catecholamine levels. If you feel that you have become very cold – take a blanket. Talk to your doctor about any concerns about testing, its risks, how it will be done, or how meaningful the results will be.
The effectiveness of the blood test
Most often, a blood test for catecholamine is performed to diagnose a tumor in the adrenal glands, called pheochromocytoma, in which the secretion of catecholamines increases tens or even hundreds of times. But blood catecholamine levels can change rapidly and be normal or below normal between attacks in patients with normal blood pressure.
In pheochromocytoma, plasma norepinephrine levels are higher than adrenaline levels. Pheochromocytomas in the adrenal glands themselves are characterized by an increase in the level of both adrenaline and norepinephrine. Outside the adrenal glands, tumors increase the level of noradrenaline only. In hypertension, the level of catecholamines in the blood is at the level of the upper limit of normal or increased by 1,5–2 times. An increase in the amount of dopamine is characteristic of neuroblastomas.
For people experiencing unusual bouts of hypertension, the best time to test is during or just after the bout. Because a number of factors, including stress from phlebotomy, can falsely increase catecholamine levels, and because hormones are rapidly eliminated from the body, blood catecholamine testing is not always accurate. For this reason, urinalysis is often performed to determine fractionated catecholamines or their metabolites.