From the Guidelines
Elevated Thyroglobulin Antibody (TgAb) levels are not directly related to thyroid cancer, but they can complicate the monitoring of thyroid cancer patients. Thyroglobulin antibodies are more commonly associated with autoimmune thyroid conditions like Hashimoto's thyroiditis. However, their presence can interfere with thyroglobulin testing, which is used to monitor for recurrence in thyroid cancer patients after treatment, as noted in the 2019 ESMO clinical practice guidelines for diagnosis, treatment, and follow-up of thyroid cancer 1.
In thyroid cancer management:
- Thyroglobulin is used as a tumor marker after thyroid removal and radioactive iodine treatment.
- If thyroglobulin antibodies are present, they can falsely lower or elevate thyroglobulin levels, making it unreliable for cancer monitoring, as seen in the guidelines for response to treatment categories in DTC patients 1.
- In such cases, alternative monitoring methods like neck ultrasounds or whole-body scans may be necessary, as suggested by the risk stratification system for the prediction of persistent or recurrent disease in DTC patients 1.
Patients with elevated thyroglobulin antibodies should inform their healthcare provider, as it may affect their cancer monitoring strategy. Regular testing of both thyroglobulin and thyroglobulin antibodies is typically recommended for thyroid cancer patients to ensure accurate interpretation of results, in line with the dynamic risk stratification approach 1.
While thyroglobulin antibodies themselves don't cause thyroid cancer, their presence can indicate an underlying autoimmune thyroid condition, which may slightly increase the risk of developing thyroid cancer over time. However, this risk is generally low, and most people with thyroglobulin antibodies do not develop thyroid cancer. The management and follow-up of thyroid cancer patients should be individualized, taking into account the presence of thyroglobulin antibodies and other risk factors, as emphasized in the 2019 guidelines 1.
From the Research
Relationship Between Elevated Thyroglobulin Antibody (TgAb) and Thyroid Cancer
- Elevated TgAb levels can be related to thyroid cancer, but they can also be caused by other factors such as exogenous immunoglobulin administration 2.
- The presence of TgAb can interfere with thyroglobulin (Tg) measurement, leading to false-positive or false-negative results, making it challenging to monitor differentiated thyroid cancer progression and recurrence 2, 3.
- A rising trend in TgAb levels can be a risk factor for recurrence of differentiated thyroid cancer, and a significant elevation of TgAb requires extended investigation 3, 4, 5.
Clinical Implications of TgAb in Thyroid Cancer Follow-up
- Neck ultrasonography (US) should be performed in patients with negative Tg-IMA but with detectable TgAb more than 6 months after initial therapy 3.
- A significant decrease in TgAb levels can represent a good prognostic sign, and patients with negative Tg-IMA and US without abnormalities who exhibit a reduction > 50% in TgAb generally do not require investigation 3, 4.
- The trend of TgAb levels can be used as a surrogate marker for disease recurrence during long-term follow-up, and a rising trend in TgAb warrants further investigation to detect recurrent disease 4, 5.
Measurement of TgAb and Tg in Thyroid Cancer Patients
- Different measurement methods, such as enzyme immunoassays (EIA), radioimmunoassay (RIA), and liquid chromatography tandem mass spectrometry (LC-MS/MS), can be used to measure TgAb and Tg, but they may have different susceptibilities to TgAb interference 6.
- LC-MS/MS methods may eliminate TgAb interference and provide more accurate Tg measurements, but they may require lower detection limits to be implemented in clinical practice 6.