Thanks for the link on amino acids. I've used tyrosine several times daily for over ten years with some good results however it has not been a fix-all.
I suspect this is due in part to the effects of heavy metals on other elements, especially iron. Iron is involved in the conversion of tyrosine to L Dopa. The body tends to keep iron low or low-norm when HMs are involved as you've probably read in Cutler and elsewhere.