Effect of moderate exercise on urinary MHPG in depressed patients.

This study attempted to clarify sources of artefact in biochemical studies with affective disorders in which 3-methoxy-4-hydroxy phenylglycol (MHPG) is used as a measurement of change in central nervous system norepinephrine (NE) turnover. Substantial increases in urinary MHPG excretion occurred in ten of the 11 patients when they increased their level of physical activity (0.5 +/- .14 mg/12 hrs versus 1.54 +/- .49 mg/12 hrs). Increases were also observed in NE (19.2 +/- 5.1 microgram/12 hrs versus 25.2 +/- 3.7 microgram/12 hrs). In four patients in whom cerebrospinal fluid MHPG levels were obtained a consistent increase of MHPG levels was observed during the activity period. Elevation of these metabolites were not correlated with changes in depression as reflected by psychiatric observation and rating scales. These data reveal a considerable amount of lability in urinary and CSF MHPG levels in the face of an unchanging affective state. They ask for careful controls for activity and stress in psychiatric patients when urinary MHPG is used as an index of central NE turnover.