VMK laboratory test (for vanillylmandelic acid) is prescribed quite often. The substance is usually found in the urine along with other hormones that are produced to combat stress by the adrenal glands. According to some observations, in patients with a tumor that secretes catecholamines, the level of this acid is higher than normal.
Definition of vanillylmandelic acid is characterized by its structure. It is the end product of the exchange of catecholamines - norepinephrine and adrenaline.
Catecholamines are synthesized in the adrenal medulla, and their entry into the bloodstream is a natural reaction of the body to mental and physical stress (fear, excitement, laughter). Norepinephrine and epinephrine are neurotransmitters that carry impulses between nerve cells. Norepinephrine promotes vasoconstriction and thus increases blood pressure levels, adrenaline speeds up heart contractions and increases metabolic ratesubstances.
An increase in vanillylmandelic acid in the urine or blood is observed in some tumors that overproduce catecholamines (pheochromocytoma, neuroblastoma).
This acid is present in the urine in a small amount, which increases after stress. Pheochromocytoma, neuroblastoma and other neuroendocrine formations are capable of producing a large amount of catecholamines, which provokes an increase in metabolic products.
Mechanism of formation of this substance
Vanillylmandelic acid is formed from norepinephrine and adrenaline not directly, but through intermediate metabolites: metanephrine, dihydroxyphenylglycol and normetanephrine. Dihydroxyphenyl glycol is formed from norepinephrine with the participation of the MAO enzyme, normetanephrine and metanephrine - from norepinephrine and adrenaline, respectively, with the participation of the COMT enzyme.
Medicine Significance
Of particular importance in clinical medical practice is given solely to how much elevated the content of vanillylmandelic acid in the urine, which may indicate the presence of pheochromocytoma. Nevertheless, there is a possibility of a false-positive diagnosis in stressful conditions. Measurement of metanephrine provides the most objective information about the absence or presence of this pathology.
Pheochromocytoma
Pheochromocytoma is a pathological neoplasm that produces adrenaline and norepinephrine. This tumor occurs inaged 30-50 years. It is predominantly benign and does not metastasize. The symptoms of pheochromocytoma are caused by the periodic release of large amounts of catecholamines into the blood. And as a result:
- a sharp increase in pressure and the complications caused by this condition (impaired circulation in the heart and brain, exacerbation of angina pectoris);
- persistent hypertension does not respond well to traditional treatment;
- severe headaches;
- palpitations;
- excessive sweating.
Pheochromocytoma is part of the MEN syndrome (multiple endocrine neoplasia, in which tumors occur simultaneously in several endocrine organs).
Surgical treatment allows you to get rid of the tumor and symptoms completely.
Neuroblastoma
Neuroblastoma is a malignant tumor of early age, most often before 2 years, 90% - before 5 years. In rare cases, it may be congenital. It originates from primitive nerve cells of the sympathetic system, is located in the abdominal cavity, on the adrenal glands, in the chest cavity, on the neck or in the small pelvis. At the time of diagnosis, in 2/3 of cases there are already metastases and germination in nearby organs.
Tumor symptoms:
- weakness, fatigue, loss of appetite, fever, behavioral disorder;
- anemia;
- joint pain;
- edema.
Research Features
For laboratory diagnostics,examining the level of vanillylmandelic acid, urine or blood is taken for analysis. The study of daily urine gives better results in comparison with the study of blood, as it eliminates the daily fluctuations in catecholamines.
Two days before the test, you can not eat vegetables, fruits, products containing vanilla sugar, cheese, chocolate, drink coffee, tea, beer. The following medications are canceled: sulfonamides (etazol, streptocid, biseptol), diuretics, acelitsalicyric acid, methyldop, iodine preparations. X-ray examinations, use of radiopaque agents and smoking are prohibited.
A positive laboratory result and an increase in the concentration of vanillylmandelic acid must be confirmed by visualization of the tumor or direct determination of the content of catecholamines in the urine.
Factors affecting the result
Failure to comply with the requirements for urinalysis for vanillylmandelic acid, improper storage of containers and untimely shipment to the laboratory can distort the results.
Factors that increase the level of a substance in the blood:
- emotional stress;
- physical activity;
- drugs and chemicals: Aymalin, Glucagon, Epinephrine, Guanethidine (in initial dosages), Levodopa (slight increase), insulin (after a high dose or insulin shock), drugs lithium, rauwolfia alkaloids, "Nitroglycerin",Aspirin, Clofibrate (dosage dependent), Labetolol, Methyldopa, Nalidixic Acid, Guaiacol, Phenazopyridine, Oxytetracycline;
- food: bananas, coffee, chocolate, tea.
Factors that reduce acid concentration:
- Chlorpromazine;
- "Debrikzovin";
- "Clofibrate" (impact depends on dosage);
- Disulfiram;
- hydrazine derivatives;
- "Guanethidine";
- Imipramine;
- "Morphine";
- MAO inhibitors.
Research objectives
The main purpose of the analysis for vanillylmandelic acid is to facilitate the diagnosis of neuroblastoma, pheochromocytoma and ganglioneuroma. The functional state of the adrenal cortex is also assessed.
Deviations from the norm
The level of vanillylmandelic acid in the urine is observed in tumors that secrete catecholamines. Follow-up studies, including urinary excretion of homovanillic acid, are recommended to diagnose and rule out pheochromocytoma. In cases where the diagnosis of pheochromocytoma is beyond doubt, the patient should be ruled out for MEN, often associated with pheochromocytoma (this disease should also be ruled out in family members of a patient with confirmed pheochromocytoma).
Reference values
These values are within:
- newborns up to 10 days of life - 1-5, 05 mg / day;
- children from 10 days to 1 year - less than 2.0mg/day;
- Children 1 to 18 years of age less than 5.0 mg/day;
- adults - 2, 1-7, 6 mg/day.
We examined how the determination of vanillylmandelic acid in urine and blood is carried out.
