• We measured plasma 3-methoxy-4-hydroxyphenylglycol (MHPG) in 13 pairs of healthy drug-free monozygotic twins. High concordance for both free and conjugated MHPG suggests that plasma levels of the metabolite may reflect a heritable biological trait. In two drug-free rapidly cycling patients studied longitudinally, plasma MHPG levels reflected alterations in psychiatric state; they were significantly higher during mania than during depression. Although largely reflecting peripheral sources, plasma MHPG level as a global index of noradrenergic function may complement urinary MHPG excretion as a probe for diagnostic subgroups or pharmacologic responsiveness in psychiatric research.
Jimerson DC, Nurnberger JI, Post RM, Gershon ES, Kopin IJ. Plasma MHPG in Rapid Cyclers and Healthy Twins. Arch Gen Psychiatry. 1981;38(11):1287-1290. doi:10.1001/archpsyc.1981.01780360103012