Thyroglobulin

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Also known as: Tg
Formal name: Thyroglobulin, Serum or Plasma

At a Glance

Why Get Tested?

To monitor treatment of thyroid cancer and to detect recurrence; less commonly, to help determine the cause of hyperthyroidism and hypothyroidism

When to Get Tested?

Prior to and after the completion of treatment for thyroid cancer, before and after radioactive iodine therapy, and at regular intervals to monitor for recurrence; it may be ordered in conjunction with other thyroid tests for certain thyroid disorders.

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

Thyroglobulin is a protein produced by the thyroid gland. This test measures the amount of thyroglobulin in the blood.

Location of the thyroid

The thyroid gland helps to regulate the rate at which the body uses energy. It is a small butterfly-shaped organ that lies flat against the windpipe in the throat and is composed primarily of very small, ball-shaped structures called follicles that produce and store thyroglobulin (Tg). Thyroglobulin then breaks down as needed into the thyroid hormones T4 (thyroxine) and T3 (triiodothyronine). The production of these hormones and their release into the bloodstream are stimulated by the pituitary hormone TSH (thyroid stimulating hormone).

Thyroglobulin is not produced by every thyroid cancer, but the most common types, the well-differentiated papillary and follicular thyroid cancers, frequently do, resulting in increased levels of thyroglobulin in the blood.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

Common Questions

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Article Sources

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Sources Used in Current Review

Hershman, J. (Revised 2012 May). Overview of Thyroid Function. Merck Manual for Healthcare Professionals [On-line information]. Available online through http://www.merckmanuals.com. Accessed August 2013.

(© 1995-2013). Thyroglobulin, Tumor Marker, Serum. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/83069 through http://www.mayomedicallaboratories.com. Accessed August 2013.

Poduval, J. (Updated 2012 October 5). Thyroglobulin. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/2089532-overview through http://emedicine.medscape.com. Accessed August 2013.

Chadwick, B. et. al. (Updated 2013 May). Thyroid Cancer. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/ThyroidCancer.html?client_ID=LTD#tabs=0 through http://www.arupconsult.com. Accessed August 2013.

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Pagana, K. D. & Pagana, T. J. (© 2011). Mosby's Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 934-935.

Clarke, W., Editor (© 2011). Contemporary Practice in Clinical Chemistry 2nd Edition: AACC Press, Washington, DC. Pp 501-502.

McPherson, R. and Pincus, M. (© 2011). Henry's Clinical Diagnosis and Management by Laboratory Methods 22nd Edition: Elsevier Saunders, Philadelphia, PA. Pp 378-379.

Spencer C. Assay of thyroid hormones and related substances. Thyroid Disease Manager. Pp 1-93. Jan 1, 2013. Available online at http://www.thyroidmanager.org/chapter/assay-of-thyroid-hormones-and-related-substances/ through http://www.thyroidmanager.org. Accessed August 2013.

Sources Used in Previous Reviews

Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.

Schlumberger, M. and Baudin, E. (1998). Serum Thyroglobulin determination in the follow-up of patients with differentiated thyroid carcinoma. European Journal of Endocrinology [On-line journal], vol (138) Pp 249-252. PDF available for download at http://www.eje.org/eje/138/0249/1380249.pdf through http://www.eje.org.

What is Thyroglobulin? John Hopkins Thyroid Tumor Center [On-line information]. Available online through http://www.thyroid-cancer.net.

Spencer, C. Thyroglobulin (Tg) and Tg Antibody (TgAb) Testing for Patients Treated for Thyroid Cancers. Thyroid Cancer Survivors' Association, Inc. [On-line article]. Available online at http://www.thyca.org/thyroglobulin.htm through http://www.thyca.org.

ARUP. Thyroglobulin and Thyroglobulin Antibody. ARUP lab [On-line testing information]. Available online at http://www.aruplab.com/guides/clt/tests/clt_215b.htm through http://www.aruplab.com.

ACS (2001 July 5). All About Thyroid Cancer, Detailed Guide. American Cancer Society [On-line information]. Available online at http://www.cancer.org/eprise/main/docroot/cri/cri_2_3x?dt=43 through http://www.cancer.org.

MEDLINEplus (2001 November 23). Antithyroglobulin antibody. MEDLINEplus [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003557.htm through http://www.nlm.nih.gov.

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(© 2005). Cancer of the Thyroid. American Thyroid Association [On-line information]. PDF available for download at http://www.thyroid.org/patients/brochures/ThyroidCancer_brochure.pdf through http://www.thyroid.org.

Whitley, RJ and Ain, KB (2004). Thyroglobulin: a specific serum marker for the management of thyroid carcinoma. Medscape from Clin Lab Med. 2004; 24(1):29-47 (ISSN: 0272-2712) [On-line Abstract] Available online at http://www.medscape.com/medline/abstract/15157556?queryText=thyroglobulin through http://www.medscape.com.

Liebert, M.A. (2003 June 05). Thyroid Tests for the Clinical Biochemist and Physician Thyroglobulin (Tg) Measurement. Medscape from Thyroid 13(1):57-67, 2003. [On-line information]. Available online at http://www.medscape.com/viewarticle/452669_print through http://www.medscape.com.

(© 2006). Thyroglobulin and Thyroglobulin Antibody. ARUP's Guide to Clinical Laboratory Testing [On-line information]. Available online at http://www.arup-lab.com/guides/clt/tests/clt_249b.jsp#1149079 through http://www.arup-lab.com.

Pagana, K. D. & Pagana, T. J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 916-918.

Clarke, W. and Dufour, D. R., Editors (© 2006). Contemporary Practice in Clinical Chemistry: AACC Press, Washington, DC. Pp 372.

Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 1030-1031.

(Revised 2009 May 14). How Is Thyroid Cancer Diagnosed? American Cancer Society [On-line information]. Available online at http://www.cancer.org/docroot/cri/content/cri_2_4_3x_how_is_thyroid_cancer_diagnosed_43.asp?sitearea=&level= through http://www.cancer.org. Accessed October 2009.

Grebe, S. (2009 March 25). Diagnosis and Management of Thyroid Carcinoma: A Focus on Serum Thyroglobulin. Medscape Today from Expert Review of Endocrinology and Metabolism [On-line information]. Available online at http://www.medscape.com/viewarticle/586810 through http://www.medscape.com. Accessed October 2009.

Hershman, J. (Reviewed 2008 June). Thyroid Disorders, Introduction. Merck Manual for Healthcare Professionals [On-line information]. Available online at http://www.merck.com/mmpe/sec12/ch152/ch152a.html?qt=thyroglobulin&alt=sh through http://www.merck.com. Accessed October 2009.

Hoofnagle, A. and Wener, M. H. (2006 December). Serum thyroglobulin: a model of immunoassay imperfection. Clinical Laboratory International, CLI-Online.com v8 [On-line information]. PDF available for download at http://www.cli-online.com/fileadmin/artimg/serum-thyroglobulin-a-model-of-immunoassay-imperfection.pdf through http://www.cli-online.com. Accessed October 2009.