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HelpTest ID 3MT 3-Methoxytyramine, 24 Hour, Urine
Necessary Information
24-Hour volume (in milliliters) is required.
Specimen Required
Patient Preparation: Tricyclic antidepressants, labetalol, and sotalol medications may elevate levels of catecholamines producing results that cannot be interpreted. If clinically feasible, it is optimal to discontinue these medications at least 1 week before collection. Levodopa (Sinemet) medication will cause false-positive results. For advice on assessing the risk of removing patients from these medications and alternatives, consider consultation with a specialist in endocrinology or hypertension.
Supplies: Urine Tubes, 10 mL (T068)
Submission Container/Tube: Plastic urine tube
Specimen Volume: 10 mL
Collection Instructions:
1. Complete 24-hour urine collections are preferred, especially for patients with episodic hypertension; ideally the collection should begin at the onset of a "spell."
2. Add 10 g (pediatric: 3 g) of boric acid or 25 mL (pediatric: 15 mL) of 50% acetic acid as preservative at start of collection.
3. Collect urine for 24 hours.
Additional Information: See Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens for multiple collections.
Secondary ID
65157Useful For
A first- and second-order screening test for the presumptive diagnosis of catecholamine-secreting pheochromocytomas and paragangliomas
Testing in conjunction or as an alternative to plasma metanephrines (PMET / Metanephrines, Fractionated, Free, Plasma) or plasma catecholamine (CATP / Catecholamine Fractionation, Free, Plasma) testing
Special Instructions
Method Name
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Reporting Name
3-Methoxytyramine, 24h, USpecimen Type
UrineSpecimen Minimum Volume
3 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Urine | Refrigerated (preferred) | 28 days |
| Frozen | 90 days | |
| Ambient | 28 days |
Clinical Information
Pheochromocytoma is a rare, though potentially lethal, tumor of chromaffin cells of the adrenal medulla that produces episodes of hypertension with palpitations, severe headaches, and sweating (spells). Patients with pheochromocytoma may also be asymptomatic and present with sustained hypertension or an incidentally discovered adrenal mass.
Pheochromocytomas and other tumors derived from neural crest cells (eg, paragangliomas and neuroblastomas) secrete catecholamines (epinephrine, norepinephrine, and dopamine). Dopamine secreting tumors are rarer than norepinephrine and epinephrine secreting tumors.
3-Methoxytyramine (3MT), metanephrine, and normetanephrine are the metabolites of dopamine, epinephrine, and norepinephrine, respectively. These metabolites are further metabolized to vanillylmandelic acid. Pheochromocytoma cells also have the ability to oxymethylate catecholamines into metanephrines that are secreted into circulation.
This test may be used as the first test for low-suspicion cases and as a confirmatory study in patients with less than a 2-fold elevation in plasma free fractionated catecholamines. This is highly desirable, as the very low population incidence rate of pheochromocytoma (<1:100,000 population per year) will otherwise result in large numbers of unnecessary, costly, and sometimes risky imaging procedures.
Reference Values
Males: ≤306 mcg/24 hours
Females: ≤242 mcg/24 hoursCautions
This test utilizes a liquid chromatography/tandem mass spectrometry (LC-MS/MS) method and is not affected by the interfering substances that affected older spectrophotometric (Pisano reaction) methods (ie, diatrizoate, chlorpromazine, hydrazine derivatives, imipramine, monoamine oxidase [MAO] inhibitors, methyldopa, phenacetin, ephedrine, or epinephrine) or acetaminophen in high-performance liquid chromatography (HPLC) methods.
This method is not subject to the known interference of acetaminophen (seen with the plasma metanephrine HPLC-electrochemical detection method).
Day(s) Performed
Monday through Friday
Report Available
3 to 5 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester