Used as a biomarker in clinical diagnostics, particularly in the assessment of neuroblastoma and other catecholamine-secreting tumors. Measured in urine and plasma, elevated levels help in monitoring disease progression and response to treatment. Also utilized in neuroscience research to evaluate dopamine metabolism, as it is the major end metabolite of dopamine degradation. Its concentration in biological fluids provides insight into central nervous system dopaminergic activity, useful in studying Parkinson’s disease, schizophrenia, and psychiatric disorders.