Your thyroid is a gland in your neck that is controlled by the pituitary gland. It produces hormones that play a role in regulating important functions such as:
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Body temperature
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digestion
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heart rate
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Mood
To check how your thyroid is working, your healthcare provider (HCP) may order the following blood tests:
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TSH
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T4
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T3
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Thyroid antibodies
What is TSH?
TSH (thyroid stimulating hormone) is a hormone that:
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Produced by the pituitary gland, located in the brain
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Tells your thyroid how much thyroid hormone to produce
What do TSH test results mean?
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Low TSH levels occur when your thyroid is overactive
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To slow down the thyroid, the pituitary gland stops producing TSH
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This is called hyperthyroidism
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Graves’ disease is the most common cause of hyperthyroidism
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High TSH levels occur when your thyroid is underactive
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To stimulate the thyroid to produce more T4, the pituitary gland produces additional TSH
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This is called hypothyroidism
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Hashimoto’s disease is the most common cause of hypothyroidism
A TSH test cannot diagnose the underlying cause of a thyroid problem.
What is T4?
T4 is thyroxine, one of the main hormones produced by the thyroid.
T4 tests are usually done along with a TSH test.
T4 is measured with:
A free T4 test
A total T4 test that measures free T4 and bound T4
What do the T4 test results mean?
Low T4 levels can be a sign of:
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Hypothyroidism
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Hashimoto’s disease
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Other thyroid diseases
High T4 levels can be a sign of:
What is T3?
T3 is triiodothyronine, one of the main hormones produced by the thyroid.
T3 tests are used to:
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Diagnose hyperthyroidism if you have symptoms
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Diagnose problems with your pituitary gland
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Monitor treatment of thyroid disease
This test is not typically used to diagnose hypothyroidism.
What do the T3 test results mean?
What are thyroid antibodies?
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If your TSH, T3, or T4 levels are abnormal, a thyroid antibody test checks whether antibodies may be attacking your thyroid.
What do the results of an antibody thyroid test mean?
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Negative = If no thyroid antibodies are found, it is most likely not an autoimmune thyroid disease.
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Positive = You may have an autoimmune thyroid disease.
Thyroid test values
Although these ranges vary by laboratory, typical adult thyroid testing ranges are:
|
Check |
Normal range |
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TSH |
0.5-5.0 mIU/L |
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Overall T3 |
80-220 ng/dl |
|
Free T4 |
0.7-1.9 ng/dl |
|
Overall T4 |
5.0-12.0 μg/dL |
Talk to your doctor
Taken together, these test results show how well your thyroid is working. Ask your HCP to help you understand the meaning of your results.
This educational resource was created with support from Immunovant, a member of the HealthyWomen Corporate Advisory Council.