Scientists Say: Hormone

This is a chemical that one part of the body uses to send a message to other body parts

a man with a beard

Adult men grow hair on their faces in part because of signals from the hormone testosterone.

Mike Mozart/Flickr (CC BY-SA 2.0)

Hormone  (noun, “HOR-moan”)

This is a type of chemical that the body uses to send a signal from one body part to another. A hormone might be made in the brain, released into the blood and travel to some distant organ, such as the kidney. At its target, this chemical will usually trigger some effect. The tissues that make hormones are part of the endocrine system. Hormones send signals that help people grow, make use of the energy in food, produce sweat and so much more.

In a sentence

When we feel threatened, our bodies release the stress hormone cortisol, which makes our heart pound and our palms sweat.

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Power Words

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cortisol   A stress hormone that helps release glucose into the blood in preparation for the fight or flight response.

endocrine system  The hormones (chemicals secreted by the body) and the tissues in which they turn on (or off) cellular action. Medical doctors who study the role of hormones in health and disease are known as endocrinologists. So are the biologists who study hormone systems in non-human animals.

hormone   (in zoology and medicine)  A chemical produced in a gland and then carried in the bloodstream to another part of the body. Hormones control many important body activities, such as growth. Hormones act by triggering or regulating chemical reactions in the body. (in botany) A chemical that serves as a signaling compound that tells cells of a plant when and how to develop, or when to grow old and die.

testosterone  Although known as male sex hormone, females make this reproductive hormone as well (generally in smaller quantities). It gets its name from a combination of testis (the primary organ that makes it in males) and sterol, a term for some hormones. High concentrations of this hormone contribute to the greater size, musculature and aggressiveness typical of the males in many species (including humans).

Bethany Brookshire was a longtime staff writer at Science News Explores and is the author of the book Pests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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