The comparison of clonidine, arginine and both combined: a growth hormone stimulation test to differentiate multiple system atrophy from idiopathic Parkinson's disease.

This study was aimed at comparing the diagnostic accuracy of the growth hormone (GH) response to clonidine, arginine and both combined in order to establish a more reliable test to differentiate parkinsonism type multiple system atrophy (MSA-p) from Parkinson's disease (PD). Twenty-four patients with MSA-p and 26 cases with PD entered the study. They were submitted to treatments of clonidine, arginine and a combination of the two in a random manner on three different nonconsecutive days.