WHAT IS TYROSINE? Tyrosine is a nonessential organic amino acid that is a building block of protein. It is a precursor of the neurotransmitter dopamine, as well as a precursor to the adrenal hormones norepinephrine and epinephrine. HOW DOES TYROSINE WORK? Tyrosine may help athletes avoid overtraining, due to its ability to offset fatigue. Because Tyrosine is a precursor of Dopamine, supplementing with Tyrosine may heighten mental alertness, increase feelings of well being, and offset physical and mental fatigue. CAN THE BODY MAKE TYROSINE? The body can make Tyrosine from the amino acid phenylalanine, but under stress anyone from athletes to the elderly can benefit from Tyrosine supplementation.