Multiple system atrophy is distinguished from idiopathic Parkinson's disease by the arginine growth hormone stimulation test.
OBJECTIVE
Multiple system atrophy (MSA) may be difficult to distinguish from idiopathic Parkinson's disease (PD). Our aim was to evaluate the accuracy of the arginine growth hormone (GH) stimulation test in distinguishing between MSA and PD in large populations of patients.


METHODS
We measured the GH response to arginine in 69 MSA (43 MSAp [parkinsonism as the main motor feature] and 26 MSAc [cerebellar features predominated]) patients, 35 PD patients, and 90 healthy control subjects. We used receiver-operating curve analysis to establish the arginine cutoff value that best differentiated between MSA and PD.


RESULTS
The GH response to arginine was significantly lower (p < 0.01) in MSA than in either PD patients or control subjects. At a cutoff level of 4 microg/L, arginine distinguished MSAp from PD with a sensitivity and specificity of 91% and MSAc from PD with a sensitivity of 96% and specificity of 91%. The arginine test had a positive predictive value for MSA of 95%. The GH response to arginine was not affected by disease duration or severity, MSA motor subtype, pyramidal signs, response to dopaminergic therapy, or magnetic resonance imaging findings.


CONCLUSIONS
The GH response to arginine differentiates MSA from PD with a high diagnostic accuracy. The results suggest an impairment of cholinergic central systems modulating GH release in MSA.
Pellecchia
Maria Teresa
MT
Departments of Neurological Sciences, University of Naples "Federico II," Naples.
Longo
Katia
K
Departments of Neurological Sciences, University of Naples "Federico II," Naples.
Pivonello
Rosario
R
Departments of Molecular and Clinical Endocrinology and Oncology, University of Naples "Federico II," Naples.
Lucetti
Claudio
C
Department of Neurosciences, University of Pisa, Pisa.
Marchese
Roberta
R
Department of Neurosciences, Ophthalmology and Genetics, University of Genoa, Genoa.
Spampani
Annalisa
A
Department of Neurology, Misericordia Hospital, Grosseto.
Manfredi
Michela
M
Neurology Unit, Poliambulanza Hospital, Brescia.
Epifanio
Antonio
A
Department of Neuroscience, Psychiatry and Anesthesiology, University of Messina, Messina.
Sensi
Mariachiara
M
Department of Clinical Neurosciences, S. Anna University Hospital, Ferrara.
Scaravilli
Tomaso
T
Department of Neuroscience, University of Padua, Padua.
Bracco
Fulvio
F
Department of Neuroscience, University of Padua, Padua.
Eleopra
Roberto
R
Department of Clinical Neurosciences, S. Anna University Hospital, Ferrara.
Morgante
Letterio
L
Department of Neuroscience, Psychiatry and Anesthesiology, University of Messina, Messina.
Donati
Edoardo
E
Neurology Unit, Poliambulanza Hospital, Brescia.
Marconi
Roberto
R
Department of Neurology, Misericordia Hospital, Grosseto.
Abbruzzese
Giovanni
G
Department of Neurosciences, Ophthalmology and Genetics, University of Genoa, Genoa.
Bonuccelli
Ubaldo
U
Department of Neurosciences, University of Pisa, Pisa.
Zappia
Mario
M
Department of Neurosciences, University of Catania, Catania, Italy.
Colao
Annamaria
A
Departments of Molecular and Clinical Endocrinology and Oncology, University of Naples "Federico II," Naples.
Barone
Paolo
P
Departments of Neurological Sciences, University of Naples "Federico II," Naples.
D000978:Antiparkinson Agents / Q000627:therapeutic use; D001120:Arginine / Q000494:pharmacology; D003937:Diagnosis, Differential; D005260:Female; D019382:Human Growth Hormone / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D019578:Multiple System Atrophy / Q000175:diagnosis*; D010300:Parkinson Disease / Q000175:diagnosis* / Q000188:drug therapy; D012372:ROC Curve; D012720:Severity of Illness Index
D000978:Antiparkinson Agents; D019382:Human Growth Hormone; D001120:Arginine