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Thyroid Tests
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Thyroid tests evaluate the function
of the thyroid gland. Too little thyroid hormone (hypothyroidism) is common
in dogs whereas too much thyroid hormone (hyperthyroidism) is common in
older cats. Because there is no single thyroid test that can diagnose all
thyroid diseases in animals, several different thyroid tests are used to
assure proper results (T4, T3, Free T4, etc.).
What Is the Thyroid Hormone,
and What are T3 and T4?
What is Thyroid Hormone?
Active thyroid hormone (nicknamed
T3, short for triiodothyronine) sets the body’s metabolic rate, sort of
like a volume dial. One might say T3 determines how hard or how fast each
cell works to do its job. Every cell of the body is affected by T3.
The thyroid glands (there’s one gland on each side of the windpipe) do
not produce T3. Instead, they produce an inactive form called T4. Tissues
of the body absorb T4 and convert it to T3.
Thyroid
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Chemical structure of human thyroid
hormones, thyroxine (T4) and triiodothyronine (T3)
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Doctors will readily make references
to T3 and T4. It is a good idea to know what they are referring to. While
T3 is the active hormone, it turns out that more meaningful information
is gained by measuring T4. Your veterinarian will probably mention monitoring
your cat’s T4 level.
Copyright 2003 - 2008 by the Veterinary Information
Network, Inc. All rights reserved.
This work was originally published by Veterinary
Information
Network, Inc. (VIN) and is republished with VIN's permission.
The above information is simply informational. It's intent is not
to replace the advice of a veterinarian nor to assist you in making a diagnosis
of your pet. Please consult with your own veterinarian for confirmation
of any diagnosis. Your pets life may depend on it.