Low levels of tyrosine can lead to deficiencies in norepinephrine and dopamine-neurotransmitters that regulate mood and depression can result.

Tyrosine deficiency is also associated with low blood pressure, low body temperature, and restless leg syndrome.

Tyrosine aids in the production of melanin (pigment responsible for hair and skin color) and in the functions of the adrenal, thyroid, and pituitary glands. Tyrosine attaches to iodine atoms to form active thyroid hormones.

A deficiency of tyrosine has been associated with hypothyroidism.

Tyrosine also acts as a mild antioxidant, suppresses the appetite, and helps to reduce body fat.

Because tyrosine binds unstable molecules that can potentially cause damage to the cells and tissues, it is considered a mild antioxidant. Thus, it may be useful in heavy smokers and in individuals exposed to chemicals and radiation.

Studies that verified tyrosine's psychological lift, even against serious cases of depression, used doses of 600-2,000 mg per day. Some people showed signs of feeling better within a week.

The drug L-dopa is usually prescribed by physicians to help control the trembling, rigidity, and other symptom's of Parkinson's disease, some research suggests that tyrosine, along with other medications, could improve the therapy.

Supplemental L-tyrosine has been used for stress reductions, and research suggests it may be helpful against chronic fatigue and narcolepsy.

L-tyrosine supplementation can help reduce PMS symptoms such as irritability, depression and fatigue.

Tyrosine may help individuals with low sex drive by stimulating the libido.