Hormone (noun)

1. A chemical substance produced by glands in the body that are responsible for regulating the metabolism, growth and development, tissue function, sexual function and reproduction, and mood.
2. A similar substance produced artificially for use as a drug.

Origin:

Early 20th century: from greek hormone "impelling", from horman "set in motion", from hormē "impulse". the word was coined by the british physiologist starling in order to describe the chemical messengers produced by the endocrine glands.

Examples:

1. Insulin is a hormone that regulates blood sugar.
2. Estrogen is a hormone that regulates the menstrual cycle.
3. Testosterone is a hormone that regulates the development of male characteristics.
4. Growth hormone is a hormone that regulates growth and development.
5. Adrenaline is a hormone that regulates the fight or flight response.