Thyroid function tests
Thyroid function tests are used to check whether your thyroid is working normally.
The most common thyroid function tests are:
- Free T4 (free thyroxine, the main thyroid hormone in your blood -- a precursor for T3)
T4
T4 (thyroxine) is the main hormone produced by the thyroid gland. A laboratory test can be done to measure the amount of free T4 in your blood. Fre...
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TSH (thyroid stimulating hormone, the hormone from the pituitary gland that stimulates the thyroid to produce T4)
TSH
A TSH test measures the amount of thyroid stimulating hormone (TSH) in your blood. TSH is produced by the pituitary gland. It prompts the thyroid g...
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Total T3 (total triiodothyronine, the active form of the hormone -- T4 is converted to T3)
T3
Triiodothyronine (T3) is a thyroid hormone. It plays an important role in the body's control of metabolism (the many processes that control the rate...
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If you are being screened for thyroid disease, often only the TSH test may be needed.
Other thyroid tests include:
- Total T4 (the free hormone and the hormone bound to carrier proteins)
- Free T3 (the free active hormone)
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T3 resin uptake (an older test that is rarely used now)
T3 resin uptake
The T3RU test measures the level of proteins that carry thyroid hormone in the blood. This can help your health care provider interpret the results ...
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Thyroid uptake and scan
Thyroid uptake
Radioactive iodine uptake (RAIU) tests thyroid function. It measures how much radioactive iodine is taken up by your thyroid gland in a certain time...
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A thyroid scan uses a radioactive iodine tracer to examine the structure and function of the thyroid gland. This test is often done together with a ...
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- Thyroglobulin
- Anti-thyroid antibody tests
The vitamin biotin (B7) can affect the results of many thyroid hormone tests. If you take biotin, talk to your health care provider before you have any thyroid function tests.
References
Faix JD. Thyroid function testing (thyrotropin, triiodothyronine, and thyroxine). In: Robertson RP, ed. DeGroot's Endocrinology. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 68.
Guber HA, Oprea M, Rusell YX. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 25.
Pearce EN, Hollenberg AN. Thyroid. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 207.
Salvatore D, Cohen R, Kopp PA, Larsen PR. Thyroid pathophysiology and diagnostic evaluation. In: Melmed S, Auchus RJ, Golfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 11.
Wassner AJ, Smith JR. Thyroid development and physiology. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 579.
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Thyroid function test - illustration
One way to evaluate the performance of the thyroid is through blood testing. The thyroid function test is a group of common tests used to evaluate how the thyroid is functioning.
Thyroid function test
illustration
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Hypothyroidism - InDepth
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Hypothyroidism
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Thyroiditis
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Iodine
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Review Date: 2/28/2024
Reviewed By: Sandeep K. Dhaliwal, MD, board-certified in Diabetes, Endocrinology, and Metabolism, Springfield, VA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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