Unfortunately you can develop a tolerance to L-tyrosine.I just saw a study on Pubmed saying it was ineffective with adhd because all the subjects got tolerance after 2 weeks.http://www.ncbi.nlm.nih.gov/pubmed/3300376
It really sucks when you think you've found something that finally works,then it fails.Been there many times.
There is another form of L-tyrosine out now(l-acetyl-tyrosine or something like that)that is suppose to be absorbed more efficiently, but tolerance may once again become a factor.
I found that L-tyrosine can be really effective when coming down from Adderall xr.(An amphetamine for adhd) It seems to really help with the depressive "blah"type of feeling that accompanies the comedown.Unfortunately I became tolerant to it (as well as the adderall!)sucks.
I do not think that people are developing a tolerance for tyrosine in the true sense of the word tolerance. I have seen it mentioned that taking too much tyrosine can actually result in retarding the release of dopamine. This obviously could be a sign of tolerance but it can also be because an imbalance in other vital nutrients has been created.
I have a theory which I am going to experiment with over the next few days, I discovered that milk contains tyrosine but that only skimmed milk for whatever reason will allow you to absorb it or turn it into dopamine, I used to drink a lot of skimmed milk when I experimented with tyrosine in the past along with DLPA, at this time I felt effects for months and not sure why i stopped taking it now, but tyrosine on its own only causes me to become depressed. I have tried it alone with the skimmed milk for the last few days and yes it seemed to be increasing dopamine levels but I've also become depressed.
To get to the point I think skimmed milk alone first thing in the morning with some good rhodiola rosea which I have been taking for over a month now, rhodiola rosea has made a massive difference to me, it really lifted me from my worst case of depression ever ive experienced, this has came about through taking duloxetine medication, I mean my worst depression episode, I believe that anyway, so anyway during this time before the rhodiola I started smoking because I needed to smoke to stop me thinking, I was going nuts but anyway since Ive stopped smoking the rhodiola does not seem to be making me feel happy, maybe this is a lot to do with stopping smoking but I'm sure it is also due to smoking cigarettes releasing masses of dopamine into my blood stream.
So now I hope that taking the skimmed milk alone with rhodiola rosea (viridian max potency) then this will increase my dopamine levels without increasing my depression also like supplementing with tyrosine has did in last few days. I think supplementing is causing imbalances in different places resulting in depression and ultimately the failure of the supplement to do anything at all.
However I still believe DLPA and Tyrosine can work together effectively for a much longer period of time but I think sticking to as natural a method as possible is the wise thing because you will look like **** with so many amino acids poisoning your system, DLPA I'm sure is toxic, it makes me look like an alien hobo sometimes thats why i dont touch it
just a tip if you want to try rhodiola dont take a full capsule, you only need a fraction maybe a a 1/3 or a 1/4