Plasma Catecholamine

Plasma catecholamines are circulating neurotransmitters and hormones—epinephrine, norepinephrine and dopamine—released by the adrenal medulla and sympathetic nerves. Measured in blood to assess sympathetic activity and to help diagnose conditions such as pheochromocytoma, autonomic dysfunction and severe stress responses. Levels change rapidly, are affected by posture, exercise and drugs, and require special sample handling because of a short half-life.

High catecholamine levels indicate increased sympathetic (fight-or-flight) activity. Causes include acute stress, severe illness, certain medications, hypoglycemia, and catecholamine-secreting tumors (pheochromocytoma/paraganglioma). Persistent elevation may produce hypertension, palpitations, sweating, headaches, tremor and anxiety. Ongoing high levels warrant medical evaluation, biochemical testing, and investigation for underlying causes.

The primary catecholamines are dopamine, norepinephrine (noradrenaline) and epinephrine (adrenaline). A fourth compound often listed is L‑DOPA (levodopa), the immediate biosynthetic precursor that contains a catechol group. For clinical testing and management, laboratories usually focus on the three endogenous catecholamines.

Before a plasma catecholamine test: tell your doctor all medicines and supplements (some must be stopped). Avoid caffeine, nicotine, alcohol, decongestants, and strenuous exercise for 24 hours. Rest quietly, lying or seated, for about 20–30 minutes before sampling; arrive calm and on time. Follow any fasting or specific medication-withdrawal instructions given by your clinician.

Urine catecholamines (often collected over 24 hours) measure cumulative excretion of catecholamines and metabolites (metanephrines, VMA), reflecting total production and useful for screening. Plasma catecholamines or plasma free metanephrines measure real‑time circulating levels, detecting acute changes. Plasma testing can be more sensitive for certain tumors but is affected by posture, stress, diet and medications, whereas urine reduces short‑term variability.

Abnormal catecholamine levels are linked to pheochromocytoma and paraganglioma (catecholamine‑secreting tumors), hypertension and related heart problems (arrhythmias, cardiomyopathy, ischemia, stress‑induced takotsubo), Parkinson’s disease (dopamine deficiency), autonomic causes of orthostatic hypotension, psychiatric conditions (anxiety, depression, ADHD), metabolic disturbances including insulin resistance and metabolic syndrome, stress‑related disorders, and drug‑withdrawal syndromes.