Andrew Huberman tends to avoid L-tyrosine because he experiences a significant crash afterward.

“but for me just by way of example l-tyrosine is something that works very powerfully to elevate my level of focus but that I tend to crash pretty hard afterward and so I tend to error away from l-tyrosine”

“The other thing about taking l-tyrosine is there is a crash. It's not a massive crash if you take it at appropriate doses and it's right for you. But it can produce a crash and a lethargy and a kind of brain fog after the next day or so.”