Norepinephrine is released from the nerve endings of the sympathetic nervous system and the adrenal medulla together with adrenaline. Its action is weaker than that of adrenaline. Norepinephrine testing is performed when there is suspicion of secondary hypertension related to the presence of a norepinephrine-producing tumor.
Noradrenaline – characteristics
Norepinephrine is a hormone belonging to the catecholamine group, released from the nerve endings of the sympathetic system and the adrenal medulla in the presence of adrenaline. Dopamine also belongs to the group of catecholamines. Norepinephrine is mainly secreted in the cells of the adrenal medulla when there is stress in the central nervous system. It leads to an increase in blood pressure due to the contraction of the muscles of the blood vessels, and is also responsible for the breakdown of glycogen, the release of fatty acids, inhibition of intestinal peristalsis and bronchodilation. Norepinephrine is less active than adrenaline. The most common indication for testing this hormone is the suspicion of the presence of a pheochromocytoma and the suspicion of neuroblastoma in children.
When do we do the norepinephrine test?
Testing the hormone norepinephrine is not a routine test. Typically, the test is performed together with other catecholamines. The most common indications for testing for norepinephrine and other catecholamines are listed below.
1. Suspicion of secondary arterial hypertension related to the presence of a tumor producing norepinephrine.
2. Suspicion of a pheochromocytoma or the exclusion of its presence. Symptoms of a possible tumor are mainly: headache, pale skin, weight loss, drenching sweats, paroxysmal blood pressure, and abnormal heart rhythms and abdominal discomfort (vomiting, constipation).
3. The examination is performed in people with a family history of pheochromocytoma.
4. Evaluation of the effectiveness of pheochromocytoma treatment. Detection of possible relapses of the disease.
5. Suspicion of neuroblastoma (neuroblastoma) in children. This condition manifests itself: shortness of breath, cough, abdominal and chest pain, weight loss of unknown origin and the presence of painless subcutaneous lumps.
6. Examination of patients with various dysfunctions in the area of the autonomic nervous system, eg with autonomic neuropathy.
7. Assessment of catecholamine secretion in tumors: adrenal and neuroendocrine.
8. Elevated norepinephrine levels also occur in people with hyperthyroidism.
Norepinephrine testing
Material for norepinephrine testing: serum or XNUMX-hour collection of urine (it is transferred to a special reservoir XNUMX hours a day; then the collected urine is mixed and sent for examination).
Preparation for the test: on an empty stomach (at least 8 hours). The concentration of norepinephrine and other catecholamines also depends on the diet, medications and stress. For this reason, it is best to limit foods such as chocolate, tea, coffee, avocado, cheese, red wine, bananas, citrus fruits and vanilla a few days before the test. It is also not recommended to drink alcohol and smoke cigarettes. In turn, drugs that may have a significant impact on the test result are: clonidine, acetaminophen, reserpine, MAO inhibitors, phenothiazines, reserpine, tricyclic antidepressants, calcium channel blockers or L-dopa.
The course of the study: one-time blood sampling from a vein in the arm.
Time to wait for the result: 1 Day.
Standard: 615-3240 pmol/l (104-548 pg/ml).
The given standards are indicative. In particular, reference values given by the laboratory where the test was performed should be followed. Incorrect results should be consulted with a specialist, especially in terms of factors that may interfere with the determination. It happens that the doctor orders another test to confirm the abnormal test result.
Factors that can reduce the levels of norepinephrine in the urine and blood include:
- autonomic neuropathies,
- autonomic disorders,
- diet and medications taken.
Remarks: Noradrenaline stimulates α-adrenergic receptors in blood vessels, which increases blood pressure. It stimulates ß-adrenergic receptors to a lesser extent, increasing the strength of the heart muscle and coronary blood flow. Norepinephrine is also produced in the central nervous system, where it influences the functions of the vegetative system, e.g. thermogenesis. There are no contraindications for the test.