Tyrosine is an amino acid precursor for synthesis of the neurotransmitters norepinephrine and dopamine. By improving the rate of neurotransmitter synthesis, tyrosine stimulates the central nervous system. It appears to function as an adaptogen by relieving physical symptoms of stress, such as mood swings. Chronically stressed individuals may not efficiently convert phenylalanine to tyrosine, making supplementation with tyrosine desirable. Tyrosine also serves as a precursor for the thyroid hormone thyroxine and melanin, the pigment responsible for skin and hair colour and protection against harmful ultraviolet rays. In addition, tyrosine stimulates growth hormone and is involved in adrenal and pituitary function. Tyrosine is also a powerful antioxidant, scavenging and neutralizing free radicals and inhibiting fat oxidation