The measurement of catecholamines (adrenaline, noradrenaline and dopamine) is used in the diagnosis of pheochromocytoma (adrenal medulla tumor) and paragangliomas (peripheral nerve neoplasms). Both of these types of neoplasms can cause paroxysmal or chronic arterial hypertension. The measurement of catecholamines is also used in the monitoring of neuroblastoma patients.
Catecholamines (adrenaline or epinephrine, noradrenaline or norepinephrine and dopamine) are found in the adrenal medulla, neurons, and brain. Their measurement is usedto help diagnose, amongst other conditions, 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, 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 synthesis of epinephrine.
Dopamine is a neurotransmitter found in the brain, the sympathetic ganglia, the liver, the lungs, the intestine and the retina. Dopamine is a product of dopa decarboxylation, acting by dilating the renal arteries, increasing the heart rate and contracting the peripheral vascular system.
Plasma catecholamines reveal the balance between their synthesis, release, uptake, catabolism and excretion. In the phaeochromocytoma, the tumor secretes increased amounts of catecholamines, causing paroxysmal or persistent hypertension. Therefore, measuring catecholamines 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 a 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 at any time during the day and may not be detected by measuring their plasma levels.
What Do Pathological Values Mean?
- Increase: Anger, electroconvulsive therapy, exercise, fear, gangloblastoma (slight increase), ganglioneuroma (slight increase), hypoglycaemia, hypotension, hypothyroidism, diabetic ketoacidosis, kidney disease, myocardial infarction (acute), neuroblastoma (slight increase), paragangliomas (slight increase), pheochromocytoma (continuous or intermittent increase), postoperative, prolonged exposure to cold, shock, stress, thyrotoxicosis. Medications: epinephrine, ethyl alcohol (ethanol, in large quantities), aspirin, decongestants, sympathomimetics, tricyclic antidepressants.
- Decrease: Alzheimer's disease, high altitude living. Medications: barbiturates, clonidine, reserpine.
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.