Source Naturals L-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 Suggested Use: 1/4 Teaspoon Daily, Mixed With Water Or Juice Between Meals Contains No Yeast, Dairy, Egg, Gluten, Corn, Soy Or Wheat. Contains No Sugar, Starch, Salt, Preservatives, Or Artificial Color, Flavor Or Fragrance Over 40 Years Of Trust. Source Naturals Was Created In 1982 By Ceo Ira Goldberg To Support Everyoneã¢ÂS Potential To Enjoy Optimal Health Manufactured In The Usa. Manufactured In Scotts Valley, Ca, Under The Good Manufacturing Practices (Cgmps) Established By The Us Food And Drug Administration (Fda) Source Naturals L-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