# Anti-Thyroglobulin Antibody Test

URL: https://thethyroidologist.com/tests/anti-thyroglobulin-antibody-test/
Section: Tests
Last medically reviewed: 2025-11-01

> The anti-thyroglobulin (anti-Tg) antibody test detects another autoimmune thyroid marker and serves as a tumour marker after thyroid cancer treatment.

The anti-thyroglobulin (anti-Tg) antibody test measures antibodies against thyroglobulin — a protein produced by thyroid cells.
It serves two purposes: detecting autoimmune thyroid disease and monitoring thyroid cancer after treatment.

## As an autoimmune marker

Anti-Tg antibodies appear in autoimmune thyroiditis alongside anti-TPO. They are less sensitive than anti-TPO for diagnosing Hashimoto’s but support the diagnosis when positive.
They are less commonly ordered alone — usually checked with anti-TPO for a complete autoimmune picture.

## As a cancer marker

After total thyroidectomy for differentiated thyroid cancer, thyroglobulin becomes a tumour marker — rising levels suggest recurrence. However, anti-Tg antibodies interfere with thyroglobulin assays, so anti-Tg levels are monitored alongside.
Persistently rising anti-Tg after cancer treatment may indicate autoimmune activity or residual disease — interpretation requires specialist context.

## Interpretation

Positive anti-Tg supports autoimmune thyroiditis when thyroid dysfunction is present. In cancer follow-up, trends matter more than absolute values — rising levels warrant investigation.
Results must be interpreted with thyroid function tests and clinical context.

## Frequently asked questions

### Why is anti-Tg checked after thyroid cancer?

Anti-Tg antibodies interfere with thyroglobulin measurement — the key tumour marker after thyroidectomy. Monitoring both ensures accurate surveillance.

### Is anti-Tg as important as anti-TPO?

For diagnosing Hashimoto’s, anti-TPO is more sensitive. Anti-Tg is complementary and particularly important in cancer follow-up.

### Can anti-Tg be positive without thyroid disease?

Rarely — low-level positivity can occur, but significant titres usually indicate autoimmune thyroiditis or post-surgical changes.

## Disclaimer

The content on this website is for general educational purposes only and does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional about your specific condition.

---
Part of The Thyroidologist — https://thethyroidologist.com