Catecholamines are proteins that are neurotransmitters, moving signals in your body and brain. They include:
They are essential to the body’s “fight-or-flight” response and help control a variety of functions, including:
- heart rate
- blood pressure
- glucose, or sugar, metabolism
- lipid metabolism
Catecholamines are primarily produced in your adrenal glands, and their levels fluctuate in response to physical and emotional stress. They can also change in response to:
- outside temperature
- blood loss
- low blood sugar
- moving from a sitting to a standing position, or vice versa
Catecholamine urine testing (CATU) is used to diagnose certain diseases that increase catecholamine production. The test is often combined with a catecholamine blood test. Levels can fluctuate, so testing generally isn’t recommended if you aren’t showing symptoms. False positive results do occur.
Why is CATU used?
A doctor usually orders CATU to look for signs of pheochromocytoma, a type of tumor that grows within your adrenal glands and makes excess catecholamines. It’s recommended that pheochromocytomas be surgically removed whenever possible, as they can interfere with regular adrenal function and cause uncontrolled hypertension. They also carry a risk of being cancerous and spreading to other organs.
In children, a CATU may be ordered if a doctor suspects the presence of a neuroblastoma. This is an aggressive nervous system cancer that often starts in the adrenal glands and can increase catecholamine levels. The sooner a child is diagnosed with a neuroblastoma, the better their chances of survival.
Your doctor will order a CATU to see if you have a pheochromocytoma, a neuroblastoma, or a paraganglioma, a group of rare nervous system tumors.
Symptoms of a pheochromocytoma are:
- high blood pressure, often on and off
- rapid heartbeat
- unusually hard heartbeat
- heavy sweating
- weight loss
- severe headaches on and off for an extended period
- pale skin
- unexplained weight loss
- strong, unexplained anxiety
It’s important to note that these symptoms don’t always indicate a pheochromocytoma. Pheochromocytomas are actually very rare tumors.
Symptoms of neuroblastoma include:
- painless blue-tinged lumps of tissue under the skin
- abdominal, chest, back, or bone pain
- abdominal mass or bloating
- swelling in the legs
- high blood pressure
- rapid heartbeat
- bulging eyeballs and other changes to the shape or size of your eyes, including the pupils
- dark areas around your eyes
- unexplained weight loss
CATU measures the amount of catecholamines in your urine. It’s usually performed over a period of 24 hours. Levels fluctuate greatly during the day.
Mayo Medical Laboratories list average levels by age as follows.
- younger than 1 year: 0.0 to 2.5 micrograms (mcg)/24 hours
- 1 year: 0.0 to 3.5 mcg/24 hours
- 2 to 3 years: 0.0 to 6.0 mcg/24 hours
- 4 to 9 years: 0.2 to 10.0 mcg/24 hours
- 10 to 15 years: 0.5 to 20.0 mcg/24 hours
- 16 years or older: 0.0 to 20.0 mcg/24 hours
- younger than 1 year: 0.0 to 10.0 mcg/24 hours
- 1 year: 1.0 to 17.0 mcg/24 hours
- 2 to 3 years: 4.0 to 29.0 mcg/24 hours
- 4 to 6 years: 8.0 to 45.0 mcg/24 hours
- 7 to 9 years: 13.0 to 65.0 mcg/24 hours
- 10 years or older: 15.0 to 80.0 mcg/24 hours
- younger than 1 year: 0.0 to 85.0 mcg/24 hours
- 1 year: 10.0 to 140.0 mcg/24 hours
- 2 to 3 years: 40.0 to 260.0 mcg/24 hours
- 4 years or older: 65.0 to 400.0 mcg/24 hours
CATU alone can’t diagnose the problem. It’s only the preliminary step in diagnosis. Further tests will be needed if you have high levels of catecholamines. These tests may include checking for byproducts of catecholamine metabolism in the urine, such as metanephrines and vanillylmandelic acid, as well as blood tests and imaging tests to look for tumors.
There’s a higher probability of a false positive test if you don’t have symptoms, and pheochromocytomas can be very hard to diagnose even if you do have symptoms.
No preparation is necessary for this test, but several things can interfere with your catecholamine level, including:
- chocolate and vanilla
- allergy medicines
- foods like walnuts, avocados, bananas, citrus, cheese, and licorice
Your doctor will give you a list of what to avoid before taking your test. Make sure to tell them all the medications you’re taking, both prescription and over-the-counter.
If your child is scheduled for CATU and you breastfeed, tell your doctor. Certain substances can pass through breast milk.
CATU will take place away from your doctor’s office, as it requires all urine collected over a 24-hour period. Follow all instructions given to you by the laboratory. You will likely be given a 3-liter bottle to collect your urine.
Typically, your 24-hour collection starts after you have urinated and disposed of the first urine of the morning.
For the next 24 hours, collect all urine as directed. Return your entire sample to the laboratory after you’ve completed the test.
To collect urine from an infant or young child, use pediatric urine bags. A bag is placed inside your child’s diaper to collect urine and replaced with a fresh one after each urination. It will come with detailed instructions.
Your test results should be ready in a couple of days. Your doctor will discuss them with you when they are available. High levels of catecholamines in your body may indicate a tumor.
A CATU abnormal result is useful in diagnosing pheochromocytoma, neuroblastoma, and paraganglioma. However, further testing will be needed to determine the type, size, and location of the tumor.