What does it measure?
Thyroglobulin is a protein made by thyroid cells. Some people form antibodies against it. Testing for these antibodies can support an autoimmune thyroid assessment and is especially important when thyroglobulin is being used after treatment for certain thyroid cancers.
Before the test
- Sample
- A blood sample from a vein.
- Purpose
- Clarify whether testing is for thyroid autoimmunity or follow-up after thyroid cancer treatment.
What can the result mean?
A positive result can occur with autoimmune thyroid disease or without an active hormone problem. It is not a cancer diagnosis. The antibodies may interfere with a thyroglobulin measurement, so an apparently low thyroglobulin result may not tell the whole story. [1] [2]
When is it useful, and how is it read?
First identify the purpose: investigating thyroid autoimmunity or monitoring after treatment for a differentiated thyroid cancer. Thyroid function matters in the first setting; thyroglobulin trends, treatment history, and assay interference matter especially in the second. [1]
What can affect it?
The reason for testing changes the interpretation. Routine thyroid-function assessment and follow-up after thyroid surgery are different situations. Method changes between laboratories can also complicate comparisons over time. [1] [2]
Antibodies can hide part of the thyroglobulin picture
These antibodies can interfere with a thyroglobulin assay. During thyroid-cancer follow-up, an apparently low thyroglobulin result needs to be read with the antibody result and the laboratory method. [1]
Questions you might have
Is this the same as thyroglobulin?
No. These are antibodies against thyroglobulin, rather than the thyroid protein itself. [1] [2]
Why measure it beside thyroglobulin?
The antibodies can interfere with thyroglobulin measurement and change how the clinician reads a follow-up result. [2]
What comes next?
Review the result with TSH and free T4 when assessing thyroid function. If it was part of cancer follow-up, your specialist will interpret antibody trends and choose a suitable thyroglobulin method or other assessments. [1] [2]
Are these antibodies relevant to thyroid function, or mainly to the reliability of my thyroglobulin result?
The reference interval and units on your report are part of understanding your result. Understand units, reference intervals, and treatment targets.
Sources & references
Medical references & original research
Books we consulted
References that informed our explanations of the test and its context.
- Pagana KD, Pagana TJ, Pagana TN. Mosby’s Diagnostic and Laboratory Test Reference. 14th ed. Elsevier; 2019.
Practical-section sources accessed: .
For general health education. Interpreting your result and deciding on tests or treatment requires your health context and a qualified clinician.
