Blood-tests Explained


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This website is intended to assist with patient education and should not be used as a diagnostic, treatment or prescription service, forum or platform. Always consult your own healthcare practitioner for a more personalised and detailed opinion

Thyroglobulin


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?

Usually none; however, depending on the laboratory method used for measurement of thyroglobulin, some dietary supplements such as multivitamins or supplements rich in vitamin B7 (Biotin) should not be taken at least 12 hours before the test is performed in order to avoid any test interference that may lead to false results.

Based on information provided by the lab, your healthcare practitioner should inform you if this or any other preparation is necessary.

The Test Sample

What is being tested?

Thyroglobulin (Tg) 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 produces hormones (thyroxine or T4 and triiodothyronine or T3) that help 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.

Thyroglobulin serves as the source of T4 and T3. The production of these hormones and their release into the bloodstream are stimulated by the pituitary hormone TSH (thyroid stimulating hormone).

Thyroglobulin is produced all healthy individuals, and normally its concentration in blood is very low. Thyroglobulin concentration increases in both benign (Graves disease, subacute thyroiditis, Hashimoto thyroiditis) and malignant conditions (thyroid adenoma, thyroid papillary and follicular cancer). Therefore, it is on one hand a non-specific indicator of a thyroid dysfunction and, on the other hand, a tumor marker that can be used to monitor patients with thyroid papillary and follicular cancer after diagnosis (see Thyroid Cancer).

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?

Usually no preparation is needed. However, depending on the laboratory method used for measurement of thyroglobulin, some dietary supplements such as multivitamins or supplements rich in vitamin B7 (Biotin) should not be taken at least 12 hours before the test is performed in order to avoid any test interference that may lead to false results.

Based on information provided by the lab, the healthcare practitioner should inform you if this or any other preparation is necessary.

The Test