Oral Phenylalanine and Tyrosine Tolerance Tests in Parkinsonian Patients

Reduction of dopamine concentrations in the brains of patients with Parkinsonism, together with reported clinical improvement after the administration of dihydroxyphenylalanine, has led to the hypothesis that impaired hydroxylation of tyrosine may be associated with the disease. To test this hypothe...

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Bibliographic Details
Published in:BMJ 1969-05, Vol.2 (5656), p.552-555
Main Authors: Braham, J., Sarova-Pinhas, Ida, Crispin, M., Golan, R., Levin, N., Szeinberg, A.
Format: Article
Language:English
Subjects:
Adult
Aged
Biochemistry
Blood
Control groups
Excretion
Female
Humans
Intestinal Absorption
Male
Metabolic diseases
Middle Aged
Older adults
Parkinson disease
Parkinson Disease - complications
Parkinsonian disorders
Phenylalanine - blood
Phenylalanine - metabolism
Preliminary Communications
Statistics as Topic
Thyroid diseases
Trajectory control
Tyrosine - blood
Tyrosine - metabolism
Xylose - metabolism
Xylose - urine
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Summary:Reduction of dopamine concentrations in the brains of patients with Parkinsonism, together with reported clinical improvement after the administration of dihydroxyphenylalanine, has led to the hypothesis that impaired hydroxylation of tyrosine may be associated with the disease. To test this hypothesis oral loading tests with L-phenylalanine and tyrosine were carried out in patients and controls. After phenylalanine lower blood levels of this were found in Parkinsonian patients than in controls, but tyrosine levels were the same. After tyrosine lower levels of this were also found in patients compared with controls. It is suggested that these findings indicate a decreased rate of tyrosine utilization in Parkinson's disease together with intestinal malabsorption; the latter is supported by the finding of abnormal D-xylose tolerance in these patients.
ISSN:0007-1447
0959-8138
1468-5833
DOI:10.1136/bmj.2.5656.552