A 660 kDa, dimeric protein produced by the thyroid gland.

Used by the thyroid gland to produce the thyroid hormones thyroxine (T4) and triiodothyronine (T3).

Produced by the thyroid epithelial cells, thyrocytes, which form spherical follicles.

It is secreted and stored in the follicular lumen.

The normal value for thyroglobulin is 3-40 ng/mL in a healthy patient.

Iodine is covalently bound to tyrosine residues in thyroglobulin molecules, forming monoiodotyrosine (MIT) and diiodotyrosine (DIT), and thyroxine is produced by combining two moieties of DIT.

Triiodothyronine is produced by combining one molecule of MIT and one molecule of DIT.

Proteases in lysosomes digest iodinated thyroglobulin, releasing T3 and T4 within the thyrocyte cytoplasm.

Levels in the blood can be used as a tumor marker for papillary or follicular thyroid cancers.

While all thyroid cancers do not produce TG it can be used as a tumor marker to evaluate the effectiveness of treatment for the most common types, papillary and follicular thyroid cancer.

Recurrent thyroid cancer results in increased levels of thyroglobulin in the blood.

Thyroglobulin levels should be evaluated prior to treatment to determine whether the cancer produces thyroglobulin, an d should be repeated serially to monitor for cancer recurrence.

About 1/4 of patients who have thyroid cancer have antibodies to thyroglobulin.

Antbodies to thyroglobulin and thyroglobulin levels should be checked because if present, they could interfere with measurement of thyroglobulin.

Levels in the blood can also be elevated in cases of Graves’ disease.

A thyroglobulin antibody test is should be done along with the thyroglobulin test.

Thyroglobulin antibodies are proteins that bind to thyroglobulin and interfere with the interpretation of the thyroglobulin test.

With the development of thyroglobulin antibodies, the thyroglobulin test results may be falsely elevated or decreased.

TG are ordered to determine the cause of hyperthyroidism and to monitor the effectiveness of treatment for Graves disease.

Rarely it may be ordered to help determine the cause of congenital hypothyroidism in infants.

Falsely high values of thyroglobulin can occur after a partial thyroidectomy because the remaining thyroid gland can increase in size.

Decreasing levels of thyroglobulin in those treated for Graves disease indicate a response to treatment.

Levels may be elevated in the presence of a goiter, thyroiditis, or hyperthyroidism.

TG is measured using enzyme-link immunosorbent assay (ELISA).

TG level should be measured every 3-6 months for two years after thyroidectomy and every 6-12 months after that for patients with thyroid cancer.

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