The serum thyroglobulin (Tg) measurements in the follow-up of patients with differentiated follicular-cell derived thyroid carcinomas, Thyroglobulin testing is also occasionally ordered to help determine the cause of hyperthyroidism and to monitor the effectiveness of treatment for conditions such as Graves disease. The thyroglobulin test is primarily used as a tumor marker to evaluate the effectiveness of treatment for thyroid cancer and to monitor for recurrence. Not every thyroid cancer will produce thyroglobulin, but the most common types, the well-differentiated papillary and follicular thyroid cancers, frequently do, resulting in increased levels of thyroglobulin in the blood.