A chemical messenger produced by cells or tissues that travels through body fluids or acts locally to regulate the activity of other cells or tissues.
Hormones coordinate many processes, including metabolism, growth, reproduction, stress responses, blood pressure, and fluid balance. Many hormones are released into the bloodstream by endocrine glands, while some are produced by other tissues.
Examples include insulin, cortisol, thyroid hormones, estrogen, and adrenaline. Hormones can act on distant organs or, in some cases, nearby or neighboring cells.
COMMONLY CONFUSED WITH
- Neurotransmitter: a chemical messenger released by a nerve cell to communicate with another nerve cell, muscle, or gland. Some substances, such as adrenaline, can function as both hormones and neurotransmitters.
- Enzyme: a biological catalyst that speeds up chemical reactions; it is not primarily a messenger.
SEE ALSO
