Thyroglobulin Test
Thyroglobulin (Tg) is a protein produced by thyroid cells — and by differentiated thyroid cancer cells. After total thyroidectomy, it becomes a sensitive tumour marker for detecting recurrence.
It is one of the most important tests in thyroid cancer follow-up.
Last medically reviewed: 1 November 2025
What it measures
Thyroglobulin is the precursor protein for thyroid hormone production. Normal thyroid tissue produces it; after total thyroidectomy, any detectable thyroglobulin suggests residual or recurrent thyroid tissue — normal or cancerous.
It is most useful after total thyroidectomy with radioactive iodine ablation, when levels should be very low or undetectable.
When it is checked
Tg is monitored periodically after thyroid cancer surgery — typically every 6–12 months for years. Levels are interpreted alongside TSH (often kept suppressed) and neck ultrasound.
A rising Tg trend is more concerning than a single elevated value — trends guide whether imaging or treatment is needed.
The anti-Tg antibody problem
Anti-thyroglobulin antibodies interfere with Tg assays — they can cause falsely low results. This is why anti-Tg antibody levels are checked alongside Tg in cancer follow-up.
If anti-Tg antibodies are present, Tg interpretation is unreliable and alternative surveillance (ultrasound, other markers) becomes more important.
Frequently asked questions
Does elevated thyroglobulin always mean cancer?
Not necessarily — residual normal thyroid tissue or benign nodules can also produce Tg. Clinical context, TSH level, and imaging determine significance.
Why is my TSH kept low during follow-up?
TSH suppression reduces stimulation of any residual thyroid tissue — a standard part of differentiated thyroid cancer surveillance.
What if I have anti-Tg antibodies?
They interfere with Tg measurement — your doctor will interpret results cautiously and rely more on ultrasound and other surveillance.
References & further reading
This page is based on established medical knowledge and guidelines from authoritative sources. Always consult a qualified clinician for personal medical advice.
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