L-Tyrosine is the direct precursor to several mood-boosting brain chemicals, including dopamine, which relaxes and sedates, and serotonin, the body’s happy neurotransmitter, which helps promote good sleep. Tyrosine is also the primary building block for the body’s two main stress related hormones, adrenaline and noradrenaline, helping to minimize the physical and physiological symptoms brought on by stress, agitation, irritability and an overwhelmed sensation.