Thyroglobulin is present in the blood of all healthy individuals at very low concentration.
If thyroglobulin concentrations are initially elevated in a person diagnosed with thyroid cancer, then it is likely that thyroglobulin can be used as a tumor marker.
Thyroglobulin levels should be undetectable or very low after the surgical removal of the thyroid (thyroidectomy) and/or after subsequent radioactive iodine treatments. However, if upon monitoring post-surgery the thyroglobulin concentration in the person's blood is still detectable, there may still be some normal or cancerous residual thyroid tissue in the person's body, indicating the need for additional treatment.
Based on the results of a thyroglobulin test, a healthcare practitioner may follow up with a radioactive iodine scan and/or radioactive iodine treatments to identify and/or destroy any remaining normal thyroid tissue or thyroid cancer. Thyroglobulin levels are then checked again in a few weeks or months to verify that the therapy has worked and monitored periodically there afterwards.
If the level of thyroglobulin is low for a few weeks or months after surgery but then begins to rise over time, then the cancer is probably recurring or spreading (metastasis).
Decreasing levels of thyroglobulin in those treated for Graves disease indicate a response to treatment.
People who have a goiter, thyroiditis, or hyperthyroidism may have elevated thyroglobulin levels, although the test is not routinely ordered with these conditions.
Anti-thyroid medications (e. g, propylthiouracil* or methimazole) can bring hyperthyroidism under control within 6 weeks to 3 months. These medications cause a decrease in the production of new thyroid hormones by the thyroid gland. Larger doses will work more quickly, but may cause side effects including skin rashes, nausea, loss of taste sensation, liver cell injury, and, rarely, a decrease of blood cell production in the bone marrow.
Radioactive iodine can destroy parts of the thyroid gland. This may be enough to get hyperthyroidism under control. In at least 80% of cases, one dose of radioactive iodine is able to cure hyperthyroidism. However, if too much of the thyroid is destroyed, the result is hypothyroidism. Radioactive iodine is used at low enough levels so that no damage is caused to the rest of the body. It isn't given to pregnant women because it may destroy the thyroid gland of the developing fetus.
Larger doses of regular iodine, which does not destroy the thyroid gland, help block the release of thyroid hormones. It is used for the emergency treatment of thyroid storm, and to reduce the excess production of thyroid hormones before surgery.