Catecholamines (Adrenaline or Epinephrine, Noreadrenaline or Norepinephrine and Dopamine) are found in the adrenal medulla, neurons, and brain. Their measurement is used, among other things, to help diagnose catecholamine-secreting tumors, such as pheochromocytoma.
Adrenaline or Epinephrine is a hormone and neurotransmitter, synthesized by the amino acid tyrosine and secreted after stimulation due to hypoglycaemia, anxiety, fear or anger. Epinephrine acts during the body's fight or flight response, dilating the bronchioles, increasing the heart rate, increasing glycogenolysis to provide more glucose and reducing peripheral resistance and blood flow to the skin and the kidneys.
Noradrenaline or Norepinephrine is a hormone and neurotransmitter and is the predominant Catecholamine. It is secreted by the adrenal medulla in response to stimulation and is also secreted by certain neurons in the peripheral nervous system. Norepinephrine is synthesized from dopamine, and in the presence of tyramine increases blood pressure through contraction of the peripheral vascular system, dilates the pupils of the eyes and relaxes the gastrointestinal tract. It also acts as an intermediate molecule in the Epinephrine synthesis.
Dopamine is a neurotransmitter found in the brain, sympathetic ganglia, liver, lungs, intestine and retina. Dopamine is a product of the decarboxylation of dopa, acting by dilating the renal arteries, increasing heart rate and contracting the peripheral vascular system.
Plasma catecholamines reveal the balance between their synthesis, release, uptake, catabolism and elimination. In the phaeochromocytoma, the tumor secretes increased amounts of catecholamines, causing paroxysmal or persistent hypertension. Therefore, measuring catecholamine levels is most useful when done during or immediately after an episode of hypertension. In normal conditions, the concentration of Epinephrine and Norepinephrine should be higher when patients are standing upright than when they are in the supine position. The absence of this difference may indicate dysfunction of the autonomic nervous system.
24-hour urine catecholamine levels are useful in detecting paroxysmal secretions that can occur during the day but can not be detected by measuring their plasma levels.
Patient Preparation for Examination
- 24-hour urine concentration is required.
- Avoid eating foods containing amines for 48 hours before testing: avocado, bananas, beer, cheese, chocolate, cocoa, fava, cereals, tea, vanilla, walnuts, wine. Also avoid drinking coffee.
- Drugs causing an increase in catecholamines should be discontinued for 48 hours. Consult your doctor.
- Avoid strenuous exercise and smoking during collection.
- Remove the collection container with the appropriate preservative (6N HCl) from the laboratory.
- Begin the collection period in the morning after the first urination, which is discarded.
- The 24-hour period begins when the first urination is rejected.
- All urine is collected for the next 24 hours in the container, which must be kept in the refrigerator.
- If any urine is accidentally lost during the 24-hour period, the test should be stopped and restarted.
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. Correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.