Tyrosine

High dietary intake of tyrosine-rich foods can elevate levels. Additionally, functional need for vitamin and nutrient cofactors for tyrosine metabolism can contribute to elevations.

Low levels of essential and conditionally essential amino acids may indicate a poor-quality diet, or maldigestion due to deficient digestive peptidase activity or pancreatic dysfunction.

Phenylketonuria (PKU) is an inborn error of metabolism involving a deficiency of the hepatic enzyme phenylalanine hydroxylase, and results in elevated phenylalanine and low tyrosine levels. Vitamin B3 deficiency has been associated with altered levels of amino acids.

Tyrosine is a conditionally essential amino acid which can come directly from the digestion of dietary protein.

Common food sources include dairy, beans, whole grains, meat, and nuts.

If intake is insufficient, tyrosine can be formed from the essential amino acid phenylalanine using a tetrahydrobiopterin reaction. Tyrosine itself is a precursor to several neurotransmitters including dopamine, epinephrine and norepinephrine. It is also needed to create thyroid hormone and melanin skin pigments.