Definition
- The catecholamines (epinephrine, norepinephrine, and dopamine) are found in the adrenal medulla, neurons, and brain. All three catecholamines are derived from tyrosine and are important neurotransmitters in the CNS and also play a crucial role in the autonomic regulation of many homeostatic functions. Other names: adrenaline, catecholamine fractionation, unconjugated dopamine, epinephrine, noradrenaline, and norepinephrine.
- Normal range: see Table 16.16.
TABLE 16 " 16Normal Range for CatecholaminesView LargeTABLE 16 " 16Normal Range for Catecholamines Age Value in pg/mL Epinephrine 2 " 10 d 36 " 400 11 d " 3 mo 55 " 200 4 " 11 mo 55 " 440 12 " 23 mo 36 " 640 24 " 35 mo 18 " 440 3 " 17 y 18 " 460 ≥18 y 10 " 200 Norepinephrine 2 " 10 d 170 " 1,180 11 d " 3 mo 370 " 2,080 4 " 11 mo 270 " 1,120 12 " 23 mo 68 " 1,810 24 " 35 mo 170 " 1,470 3 " 17 y 85 " 1,250 ≥18 y 80 " 520 Dopamine ≥2 d 0 " 20
Use
- Diagnosis of pheochromocytoma and paraganglioma, as an auxiliary test to fractionated plasma and urine metanephrine measurements.
- Diagnosis and follow-up of patients with neuroblastoma and related tumors, as an auxiliary test to urine VMA and homovanillic acid (HVA) measurements.
- Evaluation of patients with autonomic dysfunction/failure or autonomic neuropathy.
Interpretation
Increased In (Epinephrine)
- Anger, exercise, fear, burns
- Ganglioblastoma and ganglioneuroma
- Hypoglycemia
- Hypotension
- Hypothyroidism
- DKA
- Neuroblastoma
- Paragangliomas
- Pheochromocytoma
Decreased In
- Norepinephrine: anorexia nervosa
- Autonomous nervous system dysfunction
- Orthostatic hypotension
- Dopamine: possibly decreased in Parkinson disease
Limitations
- Most assays measure only free catecholamines, but a few measure both free and conjugated types. Free amines are more closely associated with tumor load than conjugated ones.
- Physiologic stimuli, drugs, or improper specimen collection slightly increases the levels. Patients should not eat, use tobacco, or drink caffeinated beverages for at least 4 hours before collection. Measurement of plasma or urine fractionated metanephrines provides better diagnostic sensitivity than measurement of catecholamines.
- Plasma levels drop quickly within 5 minutes if RBCs are not separated from plasma once collected.
- Amphetamines and amphetamine-like compounds, appetite suppressants, bromocriptine, buspirone, caffeine, carbidopa " levodopa, clonidine, dexamethasone, diuretics (in doses sufficient to deplete sodium), ethanol, isoproterenol, labetalol, methyldopa, MAO inhibitors, nicotine, nose drops, propafenone (Rythmol), reserpine, theophylline, tricyclic antidepressants, and vasodilators may interfere with this test, and the results may not be predictable.
- Children under 2 years of age show elevated response to stress.
- For accurate results, patient should be in supine for 30 minutes prior to collection.