Plasma Metanephrine

Plasma Metanephrine Test

The Plasma Metanephrine Test measures metanephrine, a metabolite of epinephrine (adrenaline), in the blood. It is primarily used to diagnose pheochromocytomas and paragangliomas, rare tumors that produce excessive catecholamines (adrenaline and noradrenaline).

Why is the Test Done?

✅ Diagnose pheochromocytomas (adrenal gland tumors)
✅ Diagnose paragangliomas (tumors outside the adrenal glands)
✅ Investigate persistent high blood pressure (hypertension) with symptoms like headaches, sweating, and rapid heartbeat
✅ Monitor patients after tumor removal for recurrence

Normal Plasma Metanephrine Levels

📌 Elevated levels suggest excessive epinephrine breakdown, often due to a catecholamine-secreting tumor.

Causes of Abnormal Metanephrine Levels

🔺 High Metanephrine Levels (>65 pg/mL) – Possible Causes

🔹 Pheochromocytoma (adrenal tumor) – Excessive adrenaline secretion
🔹 Paraganglioma (extra-adrenal tumor) – Similar to pheochromocytoma but outside the adrenal glands
🔹 Chronic Stress or Anxiety – Temporary elevation
🔹 Severe Hypertension (Uncontrolled High Blood Pressure)
🔹 Heart Disease or Heart Failure – Increased sympathetic activity
🔹 Medications – Antidepressants (MAOIs, TCAs, SNRIs), decongestants, stimulants, caffeine

📌 Very high levels (3-4 times the normal range) strongly indicate pheochromocytoma or paraganglioma.

🔻 Low Metanephrine Levels

Low levels are not clinically significant but may occur due to:
🔹 Certain medications (beta-blockers, sedatives)
🔹 Adrenal insufficiency

Symptoms of Pheochromocytoma or Paraganglioma

⚠ Episodic symptoms that come and go:
✔ Severe headaches
✔ Excessive sweating
✔ High blood pressure (often resistant to treatment)
✔ Rapid heartbeat (palpitations)
✔ Anxiety or panic attack-like episodes

Next Steps After High Metanephrine Levels

🔬 Confirmatory Tests:
✔ Plasma Nor-Metanephrine & 24-hour Urine Metanephrine Test
✔ CT/MRI Scan – To locate adrenal or extra-adrenal tumors
✔ MIBG or PET Scan – For tumor imaging if MRI/CT is inconclusive

💊 Treatment:
✔ Surgical removal of the tumor (if pheochromocytoma or paraganglioma is confirmed)
✔ Alpha-blockers (e.g., phenoxybenzamine) before surgery to control blood pressure
✔ Lifelong follow-up for recurrence or metastasis