• Twenty-four-hour urinary excretion rates of norepinephrine, normetanephrine, 3-methoxy-4-hydroxyphenylglycol, and vanillylmandelic acid were repeatedly measured in 12 depressed patients. High (>.83) positive correlations were found between the excretion rates of these four substances. Based on these findings, the conclusion was reached that in depressed patients the 24-hour urinary excretion rates of norepinephrine and any of its three major metabolites reflect total norepinephrine production in the body.
Linnoila M, Karoum F, Potter WZ. High Correlation of Norepinephrine and Its Major Metabolite Excretion Rates. Arch Gen Psychiatry. 1982;39(5):521-523. doi:10.1001/archpsyc.1982.04290050011003