Dopamine

Overview

Dopamine is a catecholamine neurotransmitter and hormone that plays key roles in motor control, reward, cognition, and regulation of prolactin and cardiovascular tone. It is synthesized from tyrosine in dopaminergic neurons and adrenal medulla cells, then metabolized mainly to homovanillic acid (HVA) and 3,4‑dihydroxyphenylacetic acid (DOPAC). Elevated circulating or urinary dopamine (and its metabolites) may be seen in catecholamine‑secreting tumors (e.g., pheochromocytoma, paraganglioma), certain drugs, or stress states, whereas low dopaminergic activity is linked to Parkinson disease and some endocrine disorders. Clinically, dopamine and its metabolites are measured mainly in the evaluation of catecholamine‑producing tumors and in research on neuropsychiatric and movement disorders.

Clinical Use Cases

  • Evaluation of suspected pheochromocytoma or paraganglioma (usually as part of a catecholamine/metanephrine panel).
  • Assessment of other catecholamine‑secreting tumors (e.g., neuroblastoma, particularly via HVA/DOPAC in urine).
  • Research measurement in Parkinson disease, schizophrenia, and other neuropsychiatric or movement disorders.
  • Monitoring dopamine infusion levels in intensive care settings (rarely by direct measurement; more often by clinical response).

Specimen Types

  • Plasma (for free catecholamines).
  • 24‑hour urine (dopamine and metabolites such as HVA).
  • Cerebrospinal fluid (CSF) in specialized research or rare diagnostic contexts.

Measurement Methods

  • High‑performance liquid chromatography (HPLC) with electrochemical detection.
  • Liquid chromatography–tandem mass spectrometry (LC‑MS/MS).
  • Immunoassays for related metabolites in some clinical laboratories.

Test Preparation and Influencing Factors

  • Often requires avoidance of catecholamine‑rich foods (e.g., bananas, chocolate, coffee, citrus, vanilla) for at least 24–72 hours before testing.
  • Many drugs affect levels (e.g., levodopa, MAO inhibitors, tricyclic antidepressants, sympathomimetics, some antihypertensives) and may need adjustment if clinically safe.
  • Stress, strenuous exercise, and smoking can transiently elevate dopamine and other catecholamines.
  • Posture and collection conditions (supine vs upright, fasting vs non‑fasting) should be standardized according to the laboratory protocol.

Synonyms

  • 3,4‑Dihydroxyphenethylamine.
  • DA.
  • Intropin (pharmaceutical dopamine hydrochloride).

Further Reading