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What is a hormone?

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Quick answer

A hormone is a chemical messenger that travels through your blood to control body processes from a distance. Made by glands, hormones regulate growth, metabolism, mood, sleep, and much more by telling distant cells what to do. It's a chemical signal released into the bloodstream.

Key things to understand

  1. It's a chemical signal released into the bloodstream.
  2. Glands (like the thyroid and adrenal) produce them.
  3. They travel to distant organs and tell them how to act.
  4. They control growth, metabolism, mood, and reproduction.
  5. Tiny amounts can have powerful, body-wide effects.

People also ask

What do hormones do?
They act as chemical messengers carried in the blood, regulating processes like growth, metabolism, mood, sleep, and reproduction.
Where are hormones made?
By glands of the endocrine system, such as the thyroid, pancreas, adrenal glands, and pituitary.
Why can small hormone changes have big effects?
Hormones are extremely potent signals, so even tiny shifts can noticeably change energy, mood, growth, or body functions.
What is insulin?
A hormone from the pancreas that controls blood sugar by letting cells absorb glucose.

Part of the guide: How Your Body Works →