October 17, 2023
Thyroglobulin is a protein that is produced by follicular cells in the thyroid gland. Most tumours that start from follicular cells in the thyroid gland also produce this protein. The follicular cells use this protein to make and store the thyroid hormones T3 and T4.
Pathologists perform a test called immunohistochemistry (IHC) to identify cells making thyroglobulin. This test helps pathologists determine if the cells they are seeing under the microscope are follicular thyroid cells. This is particularly important when examining tumour cells that have spread to another part of the body (this type of spread is called a metastasis). If the tumour cells are positive for thyroglobulin, it suggests that the tumour may have started in the thyroid gland or may be made up of cells that are behaving like cells from the thyroid gland. In contrast, if the cells are negative, it suggests that the tumour may have come from cells that do not normally produce this protein.
Doctors can also perform a test to look for this protein in the blood. This test is usually performed after someone has had their thyroid gland removed. The level of thyroglobulin decreases after the thyroid gland is removed and is usually undetectable after several weeks. Increasing protein levels in the blood after surgery may be a sign that the tumour is still present somewhere in the body.
Most types of thyroid cancer that start from follicular cells including papillary thyroid carcinoma and follicular thyroid carcinoma are positive for thyroglobulin. Noncancerous thyroid tumours such as follicular adenoma and other noncancerous conditions including nodular thyroid hyperplasia are also positive for thyroglobulin.
This article was written by doctors to help you read and understand your pathology report. Contact us if you have questions about this article or your pathology report.