The urinary excretion product measured as an indicator of epinephrine production is which metabolite?

The urinary excretion product measured as an indicator of epinephrine production is which metabolite?

• A. dopamine
• B. dihydroxyphenylalanine
• C. homovanillic acid
• D. vanillylmandelic acid

Answer: (D)

Epinephrine production is reflected in the urine by its final breakdown product through catecholamine metabolism. Epinephrine (and norepinephrine) are degraded by enzymes like COMT and MAO, forming metanephrine and normetanephrine, which are further broken down to vanillylmandelic acid. This end product, vanillylmandelic acid, is excreted in urine and has long been used as an overall indicator of catecholamine turnover, including epinephrine production. The other substances listed are upstream or unrelated to epinephrine metabolism: dihydroxyphenylalanine is an early precursor, dopamine is a neurotransmitter and its own metabolite is not a specific indicator of epinephrine production, and homovanillic acid comes from dopamine breakdown.

Epinephrine production is reflected in the urine by its final breakdown product through catecholamine metabolism. Epinephrine (and norepinephrine) are degraded by enzymes like COMT and MAO, forming metanephrine and normetanephrine, which are further broken down to vanillylmandelic acid. This end product, vanillylmandelic acid, is excreted in urine and has long been used as an overall indicator of catecholamine turnover, including epinephrine production. The other substances listed are upstream or unrelated to epinephrine metabolism: dihydroxyphenylalanine is an early precursor, dopamine is a neurotransmitter and its own metabolite is not a specific indicator of epinephrine production, and homovanillic acid comes from dopamine breakdown.