Metanephrines Plasma Test: Purpose, Normal Range, Symptoms & Tumor Detection

Overview

The Metanephrines Plasma Test is a specialized blood test used to measure the levels of metanephrine and normetanephrine in the bloodstream. These substances are metabolites, meaning they are created when the body breaks down catecholamines, which include the stress hormones epinephrine (adrenaline) and norepinephrine.

This test is especially important for detecting pheochromocytoma and paraganglioma, which are rare tumors that produce excess stress hormones. These tumors can cause dangerously high blood pressure, severe headaches, palpitations, and life-threatening complications if not diagnosed early.

Because metanephrines remain more stable in the blood than catecholamines, this test is often considered more reliable than measuring adrenaline directly.

What is the Metanephrines Plasma Test?

The test measures two major metabolites:

• Metanephrine (from epinephrine)
• Normetanephrine (from norepinephrine)

High levels of these substances may indicate that the adrenal glands or nearby nerve tissues are producing excess hormones—often due to tumors or stress-related disorders.

This test helps:

• Detect adrenal tumors
• Monitor known tumors
• Evaluate unexplained high blood pressure
• Identify causes of panic-like symptoms
• Guide treatment decisions

Doctors often use this test when a person has symptoms suggesting a hormone-secreting tumor or when imaging tests reveal a suspicious mass.

Where Are Metanephrines Produced in the Body?

Metanephrines are formed when the body breaks down catecholamines using an enzyme called COMT (catechol-O-methyltransferase).

Production occurs mainly in:

• Adrenal glands (located above the kidneys)
• Nerve tissues throughout the body
• Certain tumors (pheochromocytomas and paragangliomas)

Even when the body is resting, small amounts of catecholamines are broken down continuously, which is why low levels of metanephrines are normal.

Why is the Test Important?

1. Detects Rare But Dangerous Tumors

Pheochromocytoma and paraganglioma can lead to:

• Severe hypertension
• Stroke
• Heart failure
• Organ damage

Early detection prevents life-threatening events.

2. More Accurate Than Hormone Testing Alone

Catecholamines fluctuate rapidly with stress or movement, but metanephrines remain stable—making them more reliable markers.

3. Helps Diagnose Unexplained Symptoms

People with sudden episodes of:

• Rapid heart rate
• Sweating
• Panic
• High blood pressure

may benefit from this test.

4. Useful for Monitoring

Patients with known tumors may undergo regular testing to track changes over time.

When is the Test Recommended?

Doctors may order this test if someone has:

• Persistent or sudden high blood pressure
• Repeated episodes of palpitations
• Severe headaches
• Excessive sweating
• Tremors or shaking
• Panic-like attacks
• Flushing of the face
• A family history of adrenal tumors
• Neurofibromatosis, MEN2, or other genetic syndromes
• A suspicious adrenal mass seen on imaging

It may also be requested before certain surgeries or treatments where hormone surges could be dangerous.

Causes of Low Levels

Low levels are usually normal and not considered a medical problem.

Possible causes include:

• Low adrenal activity
• Adrenal insufficiency (rare)
• Certain medications (e.g., some blood pressure medicines)
• Very low sympathetic nervous system activity

Symptoms of Low Levels

Low levels do not typically cause symptoms and usually indicate normal body function.

Causes of High Levels

High levels can be caused by:

Medical Conditions

• Pheochromocytoma (adrenal tumor)
• Paraganglioma (tumor outside the adrenal gland)
• Neuroblastoma (a childhood tumor)

Physiological Factors

• Severe stress
• Panic attacks
• Intense physical activity
• Sleep apnea

Medications

• Antidepressants (MAOIs, TCAs)
• Stimulants
• Levodopa
• Some hypertension drugs

Other Causes

• Hypertensive crisis
• Substance use (nicotine, caffeine)

Symptoms of High Levels

High metanephrine levels often reflect excess stress hormone activity. Symptoms include:

• Sudden or persistent high blood pressure
• Rapid heartbeat (palpitations)
• Severe headaches
• Sweating episodes
• Tremors or shaking
• Anxiety or panic
• Flushed face
• Weight loss
• Fatigue (long-term cases)

Severe cases may lead to:

• Stroke
• Heart failure
• Organ damage

This requires urgent medical attention.

Reference Ranges

(May vary by lab)

• Plasma free metanephrine: < 0.5 nmol/L
• Plasma free normetanephrine: < 0.9 nmol/L

Values above the reference range may require further testing, such as urine metanephrines or imaging scans.

Sample Type

• Blood plasma, collected from a vein
• Typically after resting quietly for 20–30 minutes to minimize stress-induced hormone surges

Test Preparation

To ensure accurate results:

• Rest quietly before the test
• Avoid caffeine, nicotine, alcohol, and strenuous exercise beforehand
• Do not lie or sit upright suddenly before sampling
• Inform your doctor about:
  • Medications
  • Supplements
  • Recent stress or panic episodes

Some drugs may need to be paused (only under medical supervision).

No fasting is usually required.

When to Consult a Doctor

Seek medical help urgently if you experience:

• Sudden severe hypertension
• Chest pain or palpitations
• Severe headaches with sweating
• Seizures or fainting
• Shortness of breath
• Vision changes

Also consult a doctor if:

• You have a family history of adrenal tumors
• Lab results are significantly elevated
• Symptoms are worsening over time

Children with unexplained hypertension or headaches should be evaluated promptly.

Important Word Explanations

~END~