Blood draw
Thyroglobulin Antibodies (anti‑TG)
Anti‑TG; autoimmune thyroid.
€ 68,00
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Thyroid · Blood
Anti-Tg
Antibodies against thyroglobulin, a protein from the thyroid; found in autoimmune diseases of the thyroid.
At a glance
- Measured in blood
- In 3 test panels
- Check the preparation
Explanation
Anti-Tg: what is measured?
Thyroglobulin (Tg) is a protein that is made only in the thyroid and in which thyroid hormone is built. In an autoimmune reaction against the thyroid, the immune system can make antibodies against this protein: anti-Tg. The test measures how many of these antibodies are in the blood. In the hospital, anti-Tg is mainly measured alongside thyroglobulin, for monitoring after removal of the thyroid, because the antibodies can interfere with that measurement.
What can it detect?
- A sign of an autoimmune disease of the thyroid, such as Hashimoto's disease
- Interference with the thyroglobulin measurement by antibodies (hospital setting)
Result
What does the result mean?
Anti-Tg too high
A raised anti-Tg occurs in various thyroid diseases, especially in autoimmune diseases such as Hashimoto's disease and Graves' disease. People without thyroid disease can also have raised anti-Tg, without this having consequences. A raised value says nothing about how well the thyroid is working now; TSH and free T4 show that. With normal thyroid function, a raised anti-Tg on its own usually means nothing for treatment.
Anti-Tg too low
Most people have no anti-Tg; a low or undetectable value is normal. This does not rule out an autoimmune disease of the thyroid: in Hashimoto's disease, anti-TPO is found more often than anti-Tg.
After an abnormal result
With a raised anti-Tg, the GP looks at TSH and free T4. If these are normal, there is usually no further testing; with symptoms that point to a thyroid disorder, TSH can be measured again later.
Reliability
How reliable is the test?
Anti-Tg says nothing about how well the thyroid is working; thyroid function is determined with TSH and free T4, according to the Dutch GP guideline (NHG) on thyroid disorders. According to the Dutch Society for Clinical Chemistry (NVKC), the test is mainly intended to assess whether a thyroglobulin measurement in the hospital is reliable. As a sign of an autoimmune disease of the thyroid, anti-Tg adds little alongside anti-TPO.
What can affect the result?
- People without thyroid disease can also have raised anti-Tg.
- Reference values and cut-off values differ per laboratory and measurement method; only compare results from the same laboratory.
- The result says nothing about current thyroid function; without TSH alongside it, it is hard to interpret.
Preparation
- Do you take biotin (vitamin B8, often in hair and nail supplements)? Stop at least 2 days before the sample is taken, or 4 days for a high dose.
Who it is for
Who is the test useful for?
Useful for
The result is most meaningful in the hospital, alongside a thyroglobulin measurement after removal of the thyroid. With thyroid symptoms, TSH shows how the thyroid is working; anti-Tg says nothing about that. As a sign of an autoimmune disease of the thyroid, TSH and anti-TPO usually say more than anti-Tg.
How common is it?
An underactive thyroid affects about 3 to 4 in 100 adults in the Netherlands and an overactive thyroid about 1 in 100, both more often women. How often anti-Tg occurs in people without symptoms is not well known.
NIVEL primary care registrations and the NHG guideline on thyroid disorders
Drawbacks and risks
- A raised anti-Tg with normal thyroid function can lead to unnecessary worry or unnecessary follow-up testing.
Get tested
Anti-Tg: test panels
Anti-Tg is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.
Evidence
Sources
This explanation is based on Dutch guidelines and independent information. It is general information, not a diagnosis. Discuss an abnormal result with your GP.
More about risks and resultsMore explanations
Other tests: Thyroid
- Anti-TPO
- Free T3
- Free T4
- Reverse T3
- T3 (total)
- Thyroglobulin
- Thyroxine-binding globulin
- Total T4
- TSH
- TSH receptor antibodies (TRAb)