Thyroglobulin
Definition
Thyroglobulin is a protein produced by the thyroid gland that contributes to the regulation of functions such as heart rate and metabolism. The thyroid normally releases a small amount of thyroglobulin into the blood.
Purpose
Measured primarily as a tumor marker in thyroid cancer, especially papillary and follicular thyroid cancers. Uses include:
- Determining whether treatment removed all thyroid tissue
- Monitoring for recurrence after treatment
- Assessing the course of the disease
- Evaluating non-cancerous thyroid conditions such as hyperthyroidism and hypothyroidism
Results
After treatment:
- Very low or undetectable, suggests the thyroid tissue was successfully removed
- High or rising, suggests treatment may be incomplete or that the disease has progressed
- Rising after being low, possible recurrence
Risks and Limitations
Thyroglobulin antibodies can make the thyroglobulin level appear LOWER than it actually is. For this reason, the physician usually also orders thyroid antibody tests and switches to a different monitoring method if needed. Measurement methods vary between laboratories. For results to be comparable over time, it is important that the test is performed with the same method and generally at the same laboratory.