Hormone
Hormones do many things. They regulate metabolism. Metabolism is the chemical and energy reactions that happen in a living thing. Hormones cause the growth and death of cells and of whole organisms. Hormones also start and control sexual development. For example, the hormones estrogen and progesterone make girls go through puberty. Hormones help keep homeostasis in an organism. Homeostasis means to keep a constant state inside the body like temperature, amount of water and salts, and amount of sugar. Hormones released by one gland can also tell other glands to make different hormones.