Tyrosine is an amino acid synthesized from phenylalanine in the body. It is a precursor of the important brain neurotransmitters epinephrine, norepinephrine and dopamine, which transmit nerve impulses and are essential to prevent depression. Dopamine is vital to mental function and seems to play a role in sex drive.
Tyrosine is also used by the thyroid gland to produce one of the major hormones, Thyroxin. This hormone regulates growth rate, metabolic rate, skin health and mental health. It is used in the treatment of anxiety, depression, allergies and headaches. Animals subjected to stress in the laboratory have been found to have reduced levels of the brain neurotransmitter norepinephrine. Doses of tyrosine prior to stressing the animals prevents reduction of norepinephrine.
Human trials have been performed with soldiers placed in various forms of stress. Those soldiers receiving Tyrosine were found to perform better on a variety of tests. They were more efficient, alert and had fewer complaints. Clinical studies have shown that tyrosine can be helpful in reducing the irritation, tiredness and depression of PMS sufferers, as well as being an effective antidepressant in some more major forms of depression.
Tyrosine is used with the amino acid Tryptophan, to aid in the treatment of cocaine abuse, with some success. In one study the two amino acids were used in conjunction with the anti-depressant Imipramine to treat chronic cocaine abuse with a reported 75-80% success rate. Most of the people in the study reported that this combination blocked the cocaine high and warded off the severe depression that typically accompanies withdrawal.
Intake of Tyrosine is contraindicated for people taking antidepressants containing monoamine oxidase (MAO) inhibitors, people with high blood pressure or skin cancer. It may trigger migraine headaches. The main sources of tyrosine in the diet are meats, dairy products and eggs.