Tyrosine is an amino acid that is needed by the thyroid gland and the adrenal glands. The thyroid uses it to produce the thyroid hormones T3 and T4 (the T stands for Tyrosine). The adrenal glands also need it to produce adrenal hormones. The body does produce it, but if it is lacking in your diet, or your body is not producing enough, your energy levels and ability to deal well with stress decline. I personally am taking at this time 1 capsule of this Tyrosine in the morning and 1 capsule of NOW 5-HTP 50mg at night. These two balance each other very well. Tyrosine raises dopamine levels, 5-HTP raises serotonin levels, so by taking both supplements together it helps to keep the neurotransmitters balanced in the brain. Dr. Julia Ross has researched and written extensively on the use of these supplements both individually and together. I highly recommend reading her work for more information before deciding to use them so that you are well informed on their uses and risks. Also, they are not meant for long term chronic use because of their effects on the brain's neurotransmitters. Therefore knowledge of their actions on the body is definitely recommended before taking!