Plasma catecholamines are used as an adjunct in the diagnosis of pheochromocytoma and paragangliomas (along with the measurement of individual plasma catecholamines and total urine catecholamines) as well as in the diagnosis and follow-up of patients with neuroblastoma (together with the determination of vanillylmandelic and homovanillic acid in the urine) and in the evaluation of patients with dysfunction or insufficiency of the autonomic nervous system or autonomic neuropathy.
Catecholamines (adrenaline or epinephrine, noradrenaline or norepinephrine, and dopamine) are produced 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 hypoglycemia, anxiety, fear, or anger. Epinephrine acts during the body's fight or flight response resulting in dilation of the bronchioles, increased heart rate, increased glycogenolysis to provide more glucose, and the reduction of 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 synthesis of epinephrine.
Dopamine is a neurotransmitter found in the brain, sympathetic ganglia, liver, lungs, intestine, and retina. Dopamine is a product of dopa decarboxylation, acting by dilating the renal arteries, increasing the heart rate, and contracting the peripheral vascular system.
The levels of catecholamines reveal the balance between their synthesis, release, uptake, catabolism, and elimination. In 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 during the day but can not be detected by measuring their plasma levels.
Possible Interpretations of Pathological Values
- Increase: Adrenal cortex adenomas, burns, exercise (intense), ganglioneuroma, neuroblastoma, pheochromocytoma, epileptic seizures (tonic-clonic), catecholamine-secreting tumors, stress (anger). Medications: Caffeine, ethyl alcohol (ethanol) (large quantities), reserpine (short-term use), sympathomimetics
- Decrease: Anorexia nervosa, familial dystonia, idiopathic and orthostatic hypotension. Medications: Guanethidine sulfate, phenothiazines, reserpine (chronic use)
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. The 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.
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