Thyroglobulin

Latest Edit: Hector 2014-03-21 (EDT)

See Also	Lab Tests

This test is used as a primary tumor marker for well-differentiated thyroid cancer.

Discussion

• Thyroglobulin or Tg, is the protein precursor of thyroid hormone. It is made by normal well-differentiated benign thyroid cells or thyroid cancer cells.
• Since Tg is only made by thyroid cells, it allows for the detection of the presence or absence of thyroid cells, particularly after thyroid cancer surgery.
• Tg is also used as a tumor marker in postoperative patients, as it is a marker of disease activity and the volume of thyroid tumor. Ideally, Tg levels will be low or undetectable after treatment (usualyl surgery followed by radioactive iodine).

Patient Preparation

• No fasting required.

• Factors which can cause increased levels

• Thyroglobulin autoantibodies

• Factors which can cause decreased levels

• Less well-differentiated thyroid cancers, patients whose tumors do not have TSH receptors or whose tumors cannot make Tg, thyroglobulin autoantibodies

Clinical Implications

High levels indicate:

• Residula thyroid tissue in the neck
• Metastatic thyroid cancer

Associated Tests

• Antithyroglobulin antibody