Hormones are called chemical messengers because they are chemical agents that travel around the body to tell specific cells to perform a specific action. The term hormone describes a variety of chemicals that perform these signaling tasks. Hormones can range from proteins to amino acids to steroids.
The body has an endocrine system that is comprised of several glands. Glands secrete hormones when given a signal from the brain. Hormones are needed for a range of activities. Some signal appetite when cells need energy, while others signal sex drive when sperm or eggs are created. Hormone molecules go in search for certain cells, and when they find the right one with the right hormone receptor, it instructs the cell to begin the process.