24-hour urinary metanephrines
This test measures the amount of metanephrines in your urine that your body makes over a 24-hour period.
Metanephrines are made when your body breaks down hormones called catecholamines. These hormones are made by the adrenal glands. Catecholamines help your body respond to stress. They are sometimes called "fight or flight" hormones. They also include epinephrine, norepinephrine, and dopamine.
You may need this test if your healthcare provider suspects you have a condition called pheochromocytoma or paraganglioma. These are rare tumors that make extra amounts of catecholamines. Pheochromocytomas are found in the adrenal glands. Paragangliomas are found outside the adrenal glands.
Signs and symptoms of pheochromocytoma or paraganglioma include:
High blood pressure
Your healthcare provider may also order a blood test that measures metanephrines, called a fractionated plasma metanephrine test. Other byproducts of catecholamines may also be measured.
Test results may vary depending on your age, gender, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you.
Total urinary metanephrines can be measured in milligrams (mg). A level of 1.3 mg or greater over 24 hours is often considered positive.
Different labs have different ways of measuring catecholamine levels. Your healthcare provider will discuss your results with you.
If your 24-hour metanephrine level is between 1 and 2 times the normal amount, there is about a 30% chance you have a pheochromocytoma or paraganglioma.
If your 24-hour metanephrine level is twice the normal level or higher, it's likely that you have a pheochromocytoma or paraganglioma. You may need to have imaging tests, including CT or MRI scans. These tests are done to confirm the diagnosis and find the tumor.
This test needs a 24-hour urine sample. For this sample, you must collect all of your urine for 24 hours. Empty your bladder completely first thing in the morning without collecting it. Note the time. Then collect your urine every time you go to the bathroom over the next 24 hours.
Your healthcare provider will probably give you specific instructions. Follow them carefully.
This test poses no known risks.
Certain medicines, foods, and conditions can cause metanephrine and catecholamine levels to be higher than normal. These include:
Antidepressants and amphetamines
Physical or emotional stress
Withdrawal from drugs or alcohol
Obstructive sleep apnea
Don't drink anything containing caffeine before or during the test. Tell your healthcare provider if you are taking medicine, and ask whether you have any food, medicine, or activity restrictions. Be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.
Plan to be home for the 24 hours you do the test so you can store the urine sample properly.