The primary functions of L-Tyrosine in the body are to help produce catecholamines like dopamine and adrenaline. L-Tyrosine is also important to the proper function of the thyroid. The connection to the function of the thyroid leads to one of the important uses of L-Tyrosine as a supplement for weight loss and weight control. 

There is current research that shows that L-tyrosine can help improve brain function. For example, one study that tracked the effects of L-tyrosine supplements on healthy college students found that those who had taken the supplement demonstrated marked improvements in memory and focus over test subjects who had been given a placebo. 

L-tyrosine has been shown to provide increased energy and endurance. This is great for all athletes and for anyone who works out regularly. These results are especially encouraging for endurance athletes like runners.