A free-form amino acid which rapidly crosses the blood-brain barrier</br>Dietary supplement</br>Available in powder form</br></br>Product Description</br></br>Dietary supplement. L-Tyrosine is a free-form amino acid which rapidly crosses the blood-brain barrier. It is precursor for the neurotransmitters dopamine?? norepinephrine?? and epinephrine?? for thyroid hormones?? and for enkephalins?? special peptides which</br><br/>http://www.amazon.com/gp/product/B001G7R4MI