Oral Phenylalanine and Tyrosine Tolerance Tests in Parkinsonian PatientsBr Med J 1969; 2 doi: https://doi.org/10.1136/bmj.2.5656.552 (Published 31 May 1969) Cite this as: Br Med J 1969;2:552
- J. Braham,
- Ida Sarova-Pinhas,
- M. Crispin,
- R. Golan,
- N. Levin,
- A. Szeinberg
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.
Log in using your username and password
Log in through your institution
Register for a free trial to thebmj.com to receive unlimited access to all content on thebmj.com for 14 days.
Sign up for a free trial