
Dietary Supplement Free Form Amino AcidL-Tyrosine is a free-form amino acid which rapidly crosses the blood-brain barrier. It is a precursor for the neurotransmitters dopamine, norepinephrine, and epinephrine, for thyroid hormones, and for enkephalins, special peptides which subdue messages of physical discomfort. L-Tyrosine is also a precursor for the protective skin pigment melanin.