Noradrenaline is a hormone from the catecholamine group, which also includesadrenalineanddopamine. It is secreted primarily in the cells of the adrenal medulla under stress and in the central nervous system. Norepinephrine acts on adrenergic receptors, exerting multidirectional effects on various systems of the human body. It causes an increase in blood pressure due to the contraction of the blood vessel muscles, the release of free fatty acids from fat cells, the breakdown of glycogen (a reserve substance), bronchodilation, and inhibition of intestinal peristalsis.
It is present in the blood serum, it is excreted in the urine unchanged and in the form of metabolites.
In this article, Niketrainers.com.co will tell you:
What are the indications for norepinephrine testing?
Norepinephrine testing is not routinely performed. Usually, its determination is carried out together with other catecholamines. Indications for testing norepinephrine and other catecholamines:
- confirmation or exclusion of a pheochromocytoma, suspected in the case of symptoms such as:
– paroxysmalarterial hypertension, less permanent
– headaches
– drenching sweats
– pale skin
– orthostatic hypotension, i.e. a sudden drop in blood pressure after standing up, i.e. changing the body position from lying to standing
– abdominal pain, nausea, vomiting,constipation
– unexplained weight loss
– heart rhythm disturbances - suspected neuroblastoma, especially in children:
– pain in the abdomen, chest, back, bones
– painless subcutaneous nodules
– unexplained weight loss
–cough,shortness
of breath – low-grade fever - evaluation of the effectiveness of treatment of pheochromocytoma, evaluation of recurrences
- evaluation of catecholamine secretion in neuroendocrine and adrenal tumors
- in people with a strong family history of pheochromocytoma
- assessment of patients with dysfunctions within the autonomic nervous system, with autonomic neuropathy.
How is norepinephrine tested?
The concentration of norepinephrine is assessed in the blood serum or in a 24-hour urine collection. In the case of a blood test, it is sufficient to take a sample, usually from a vein in the arm.
The 24-hour collection of urine consists in urinating 24 hours a day into a specially prepared tank (urine collected during the day is stored in a refrigerator). Then the collected urine is mixed and the collected sample is sent for testing.
How to prepare for the norepinephrine test?
Patients for blood norepinephrine testing should report on an empty stomach (interval from the last meal approx. 8 hours). The concentration of catecholamines (including noradrenaline) depends on the medications taken, stress and diet. In the case of a daily urine collection and before blood tests, it is best to limit foods for a few days, such as:
- coffee, tea, chocolate, cocoa – containing caffeine
- bananas, nuts, avocados, cheese, red wine – rich in so-called tyrosine, i.e. an amino acid from which it is made, among others noradrenaline
- citrus fruits, vanilla.
You should also refrain from consuming alcohol and smoking. In the case of drugs that affect the concentration of catecholamines, it is necessary to consult a doctor and jointly analyze the pharmaceuticals taken.
Drugs and substances that may increase or decrease the concentration of catecholamines:
- acetaminophen
- aminophylline
- buspirone
- calcium channel blockers
- phenothiazines
- anesthetic gases, e.g. halothane
- MAO inhibitors
- clonidine
- L-dopa, methyldopa
- pseudoephedrine
- reserpine
- tricyclic antidepressants.
What are the contraindications for norepinephrine testing?
There are no contraindications for blood and urine norepinephrine testing.
Interpretation of the norepinephrine test results
Nominal concentration of norepinephrine in the blood: supine position 70–750 pg / ml, standing position 200–1700 pg / ml
The norm of urine norepinephrine concentration: 15–80 µg / day (89–473 nmol / day)
The presented standards are indicative, one should follow the standards presented by the laboratory performing the particular test. The results of the catecholamine test are influenced by the medications taken, diet and stress, therefore the incorrect results are carefully analyzed by the doctor in terms of factors that may disturb the test. Repeat testing is often performed to confirm abnormal results.
The reasons for the increase in the concentration of norepinephrine in the urine and peripheral blood:
- phaeochromocytoma (but its adrenal or extra adrenal location or size cannot be estimated from catecholamine levels)
- neuroblastoma
- overactive thyroid gland
- stress
- medications and foods taken.
Reasons for the decrease in the concentration of norepinephrine in the urine and peripheral blood:
- autonomic disorders
- autonomic neuropathy
- Medications and foods are taken.