Thyroid-Stimulating Hormone (TSH)
Thyroid-stimulating hormone (TSH) is produced by the pituitary gland, which is located in the brain. TSH stimulates the release of T3 and T4 by the thyroid, a gland in the neck. These hormones help control the rate at which the body uses energy.
| What is the purpose of this test? | The TSH test is used to:
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| How to prepare? |
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| Reference values* |
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| Associated tests |
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| How it is done? | Blood sample, usually taken from a vein in the arm. |
| How long before I get the results? | Results are usually ready in a day. It may take longer to receive your results. |
What does an abnormal test result mean?
High TSH levels:
- Hypothyroidism (underactive thyroid gland)
- Rare TSH-secreting tumour of the pituitary gland
- Underuse of thyroid hormone drugs used to treat hypothyroidism
- Excessive intake of antithyroid drugs
Low TSH levels:
- Hyperthyroidism (overactive thyroid gland)
- Damage to the pituitary gland that inhibits TSH production
- Excessive use of thyroid hormone drugs
- Underuse of antithyroid drugs in people with hyperthyroidism
Medications that may affect test results
Certain medications may affect test results. Here are a few examples:
- Amiodarone
- Fluoxetine
- Lithium
- Lamotrigine
Factors that can interfere with test accuracy
Biotin taken as a dietary supplement may interfere with thyroid hormone and TSH measurements. It is recommended to stop using biotin supplements for at least 2 days before undergoing thyroid-related laboratory tests, such as TSH and T3 and T4 tests.
What you should know before going for this test
When you go in for a blood test or any other medical exam, it's always a good idea to bring a complete list of any prescriptions, over-the-counter medications, or natural health products you're taking. Unless otherwise advised, it's best to take your medications as usual on blood test days. If in doubt, don't hesitate to talk to your healthcare professional.
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The patient information leaflets are provided by Vigilance Santé Inc. This content is for information purposes only and does not in any manner whatsoever replace the opinion or advice of your health care professional. Always consult a health care professional before making a decision about your medication or treatment.