Hormones (from Greek ὁρμή - "impetus") are chemicals released by cells that affect cells in other parts of the body. Only a small amount of hormone is required to alter cell metabolism. It is essentially a chemical messenger that transports a signal from one cell to another. (from Wikipedia)
This second video Dr. Mark Hyman explains in a simple way - why we so often experience ups and downs - physically and emotionally - and how to achieve more balance by simply eliminating things like corn syrup from our diets.