Elevated platelet norepinephrine concentration in patients with pheochromocytomas

Area of Science:

• Endocrinology
• Biochemistry
• Oncology

Background:

• Pheochromocytoma diagnosis can be challenging, especially in normotensive patients.
• Plasma norepinephrine levels are not always elevated in pheochromocytoma.
• Radioenzymatic assays offer a method for norepinephrine analysis.

Observation:

• Simultaneously measured plasma and platelet norepinephrine concentrations were analyzed in six pheochromocytoma patients.
• Elevated platelet norepinephrine was observed in all six patients preoperatively or intraoperatively.
• Three patients had normal plasma norepinephrine levels, while platelet levels were elevated.
• Following tumor resection, five patients showed normalized platelet and plasma norepinephrine.
• One patient with malignant pheochromocytoma maintained elevated levels post-surgery.

Findings:

• Platelet norepinephrine concentration is a sensitive indicator for pheochromocytoma.
• Elevated platelet norepinephrine was found in 27% of hypertensive patients without pheochromocytoma (diastolic BP ≥ 120 mmHg).
• Normotensive pheochromocytoma patients exhibited elevated platelet norepinephrine.
• Only 8% of non-hypertensive 'sick' patients had elevated platelet norepinephrine.

Implications:

• Platelet norepinephrine concentration serves as an effective screening test for pheochromocytoma, particularly in patients with a history of hypertensive spells but currently normotensive.
• An elevated platelet norepinephrine result warrants further investigation with 24-hour urine collection for vanillylmandelic acid (VMA) and/or catecholamines.
• This assay can aid in early detection and management of pheochromocytoma.