Tyrosine is a non-essential amino acid that is synthesized in the body from phenylalanine. As a building block for several important brain chemicals, tyrosine is needed to make epinephrine, norepinephrine, serotonin, and dopamine, all of which work to support mood. Tyrosine also aids in the function of organs in the body responsible for making and regulating hormones, including the adrenal, thryroid, and pituitary glands.