%0 Journal Article
%T High concentration of plasma methoxytyramine: dopamine
%A Bettina Winzeler
%A Eric Grouzmann
%A Haithem Chtioui
%A Karim Abid
%A Oliver Tschopp
%A Samira M Sadowski
%J Annals of Clinical Biochemistry
%@ 1758-1001
%D 2019
%R 10.1177/0004563219835263
%X Levodopa (L-DOPA) provided to patients with Parkinson¡¯s disease causes an increase in dopamine and methoxytyramine blood concentration which may lead to erroneous diagnosis of dopamine-producing tumours based on a plasma fractionated metanephrines and methoxytyramine assay. Considering that oral L-DOPA is mainly transformed in the gut wall into dopamine and methoxytyramine, we hypothesize that patients treated with L-DOPA produce predominantly sulphated methoxytyramine, whereas dopamine-producing tumours, devoid of sulfotransferase, will secrete free methoxytyramine. These metabolic differences may allow for discrimination between the two groups of patients through methoxytyramine plasma concentration. We retrospectively investigated a cohort of 16 patients with a dopamine-secreting pheochromocytoma or paraganglioma and 22 patients treated for Parkinson¡¯s disease to see whether the metabolic ratio of free and sulphated methoxytyramine differs. Receiver operating characteristic curve analysis indicates an absolute separation between the two groups when using a cut-off of free/total methoxytyramine (sum of free and sulphated methoxytyramine) ratio of 0.0059, corresponding to a free methoxytyramine fraction of 0.59% (P£¿<£¿0.0001, AUC 1.0 indicating 100% sensitivity and specificity). Dopamine secreted by tumours and exogenous dopamine (from Parkinson¡¯s disease treatment) follow different metabolic pathways. We observed that free/total methoxytyramine ratio may be a useful tool in distinguishing between patients with a dopamine-secreting tumour from patients treated with L-DOPA when clinical information is incomplete or lacking
%K Catecholamines
%K tumour markers
%U https://journals.sagepub.com/doi/full/10.1177/0004563219835263