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Also known as: Tg
Formal name: Thyroglobulin

At a Glance

Why Get Tested?

To monitor treatment of some types of thyroid cancer and to detect recurrence

When to Get Tested?

Once treatment for thyroid cancer has been completed, before and after radioactive iodine therapy for thyroid cancer, and at regular intervals to monitor for recurrence

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?


The Test Sample

What is being tested?

The thyroid gland is composed mainly of very small, ball-shaped structures called follicles. Thyroid follicle cells produce and store the thyroid hormones T4 or thyroxine and T3 or triiodothyronine as part of a protein called thyroglobulin, which occupies most of the centre of a follicle. When needed, the thyroglobulin is broken down to release thyroid hormones. No other part of the body makes this protein. Many thyroid cancers release small amounts of thyroglobulin into the bloodstream and this is what is measured by this test.

How is the sample collected for testing?

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

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

No test preparation is needed.

The Test

Common Questions

Ask a Laboratory Scientist

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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.


Pacini F et al. Thyroid cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Ann Oncol 2012; 23 (Supp 7) vii110 – vii119.