Thyroglobulin (Tg) blood test

What is being analysed in a thyroglobulin (Tg) blood test?

Thyroglobulin (Tg) is a protein produced by the thyroid gland. In medical diagnostics, the level of thyroglobulin in the blood is analysed to assess thyroid health, particularly in individuals who have undergone thyroid cancer treatment or thyroidectomy.

 

What does the result mean?

The thyroglobulin level in the blood can indicate the presence or recurrence of thyroid cancer. Elevated levels may suggest the presence of thyroid tissue, indicating potential cancer recurrence or metastasis.

 

Why perform the analysis?

This blood tear is crucial for monitoring thyroid cancer patients after treatment. It helps in the early detection of cancer recurrence or metastasis, enabling timely intervention and management.

 

When should the analysis be done?

Thyroglobulin analysis is typically performed at regular intervals following thyroid cancer treatment, such as thyroidectomy or radioactive iodine therapy. The frequency of testing may vary based on individual patient characteristics and the clinical judgment of healthcare providers.

 

What sample is required?

A blood sample is required for thyroglobulin analysis. The sample is usually drawn from a vein in the arm using standard venipuncture techniques. In addition to blood tests, imaging studies such as ultrasound or radioiodine scans may also be used in conjunction with thyroglobulin analysis to assess thyroid cancer status.

 

Is any prior preparation necessary?

Prior preparation for thyroglobulin testing may include fasting for a specific duration before the blood draw, as instructed by the healthcare provider. Patients should follow any specific instructions provided by their healthcare team.

 

What are the normal values?

Normal thyroglobulin levels vary depending on factors such as age, gender, and the presence or absence of thyroid cancer. Generally, thyroglobulin levels are considered low or undetectable (<0.2 ng/mL) in individuals who have undergone total thyroidectomy and ablation therapy.

Thyroglobulin values (ng/mL)

Situation

Thyroglobulin Level

Normal (non-thyroid cancer)

<0.2

Thyroid cancer surveillance

Variable, >0.2

Suspected recurrence

Elevated

Post-treatment monitoring

Undetectable/low

 

What does having altered values indicate?

Elevated thyroglobulin levels may indicate thyroid cancer recurrence, residual thyroid tissue, or metastasis. Conversely, undetectable or low thyroglobulin levels in thyroid cancer patients following treatment are indicative of a favourable response to therapy and the absence of detectable cancer.