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a combining form representing thyroid in the formation of compound words: thyrotropin.
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Also especially before a vowel, thyr-.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022


What does thyro- mean?

Thyro- is a combining form used like a prefix representing the word thyroid. The thyroid gland is located in the neck and produces hormones regulating the body’s growth, development, and metabolism. It is often used in medical terms, especially in anatomy and pathology.

Thyro- comes from the Greek thyreoeidḗs, meaning “shield-shaped,” based on thyreós, a kind of oblong shield used by ancient Greek soldiers. Learn more about the origins of this word at our entry for thyroid.

What are variants of thyro-?

When combined with words or word elements that begin with a vowel, thyro- becomes thyr-, as in thyrosis.

Examples of thyro-

One example of a medical term that features the combining form thyro- is thyrotomy, “incision or splitting of the thyroid cartilage.”

The first part of the word, thyro-, means “thyroid.” The second part of the word, the combining form -tomy, means “incision.” Thyrotomy literally translates to “thyroid incision.”

What are some words that use the combining form thyro- or thyr-?

What are some other forms that thyro- or thyr- may be commonly confused with?

Not every word that begins with the exact letters thyr- is necessarily using the combining forming thyr- to denote “thyroid.” The botany term thyrsus or thyrse, for example, has a very different origin. Learn what a thrysus is at our entry for the word.

Break it down!

The combining form -tome means “cutting instrument.” With that in mind, what is a thyrotome?

How to use thyro- in a sentence

British Dictionary definitions for thyro-


before a vowel thyr-

combining form
thyroidthyrotoxicosis; thyrotropin
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012