I'm sorry for any confusion, but "Methyltyrosines" is not a widely recognized medical term or concept in the field of medicine or biochemistry. It seems that there might be some misunderstanding or typo in your question.

If you are referring to "3-Methoxytyrosine" or "3-MT," it is a metabolite of dopamine, which is formed in the body by the enzyme catechol-O-methyltransferase (COMT). 3-MT can be measured in various biological samples, such as urine or plasma, to evaluate the activity of COMT and assess the exposure to drugs that inhibit this enzyme.

If you meant something else by "Methyltyrosines," please provide more context or clarify your question so I can give a more accurate answer.