Adrenal Gland cont., VMA

V.M.A Generally, unfortunately most of the hormones are present in blood in such small amounts that their measurement is very difficult. Some of hormones or their metabolites are excreted in the urine and in many instances their concentration in urine is much greater than in blood. Since it is much easier to obtain a few hundred milliliters of urine, than, say,20 ml of blood, some hormone analysis may be done with urine. Since the hormone excretion rate may vary during the day. The use of a 24 hour urine specimen gives more accurate results. يضع الكونتينر اللي بحمع فيه بالتلاجة

Not all hormones are excreted in the urine in appreciable amounts, those of lower molecular weight, e.g. the steroids, are more likely to be found in the urine in measurable amounts than are larger molecules such as the pituitary hormones. In some instances the hormone itself may not be excreted in the urine in large quantities, but various metabolites of the hormone may be found. The measurement of these metabolites sometimes gives satisfactory estimate of the amount of original hormone present in the blood.

Vanillylmandelic Acid, 24 hr urine. Vanillylmandelic acid (VMA) is one of the metabolites of the catecholamines epinephrine (adrenaline) and norepinephrine. This test measures the amount of VMA that is excreted into the urine, typically over a 24-hour period, to detect excess catecholamine production.

Useful For Screening children for catecholamine-secreting tumors.   Supporting a diagnosis of neuroblastoma Monitoring patients with a treated neuroblastoma The measurement of urinary metanephrines plus VMA have been suggested as the best screening procedure for the detection of pheochromocytomas. Pheochromocytoma tumor located in one or both of the adrenal glands that releases excess hormones called catecholamines (e.g., dopamine, epinephrine (adrenaline), norepinephrine and their metabolites, such as metanephrines) Metanephrin a metabolite of epinephrine(adrenaline)

VMA is usually present in the urine in small fluctuating amounts that only increase appreciably during and shortly after the body is exposed to a stressor. (24 hr is the best) Neuroblastomas, pheochromocytomas, and other neuroendocrine tumors, however, can produce large amounts of catecholamines, resulting in greatly increased concentrations of the hormones and their metabolites. The hormone releases can cause persistent hypertension, severe headaches, palpitations, sweating, nausea, anxiety, and tingling in the extremities.

Patient preparation: Patients should avoid for 72 hours prior to collection salicylates, caffeine, phenothiazine and antihypertension agents. Also coffee, tea, chocolate, fruit (especially bananas and any vanilla containing substances).   Collect 24-hour urine. Refrigerate 24-hour specimens during collection.     Storage/Transport Temperature Refrigerated.   Unacceptable Conditions: Specimen types other than urine.   Stability Ambient: Unacceptable; Refrigerated: 1 week; Frozen: 2 weeks  

Preferred Specimen(s) : 10 mL of a 24-hour urine collected with 25 mL 6N HCl, submitted in a leak-proof urine container Minimum Volume : 5 mL Alternative Specimen(s) : Unpreserved 24-hour urine with pH <6 Collection Instructions 10 mL urine: pH adjusted to < 3.0, using 6N HCl. Urine without preservative is acceptable if pH is below 6 and the sample is shipped frozen. Transport Temperature: -Preserved: Room temperature -Unpreserved: Frozen

Specimen Stability: Room temperature: 10 days  Refrigerated: 14 days Frozen: 1 year Reject Criteria: pH >3.0 Received unfrozen Methodology High Performance Liquid Chromatography (HPLC) Clinical Significance: Urinary vanillylmandelic acid is useful in diagnosing neuroblastoma, one of the most common tumors in the pediatric population

Phosphate buffer

NACL NACL K2Co3 MP Na MS Na

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