What this test measures
The Anti-Thyroid Antibody (ATAB) Panel measures the two principal thyroid autoantibodies:
• Anti-TPO (Thyroid Peroxidase Antibody) — directed against the enzyme that synthesises thyroid hormones; the most sensitive single marker of Hashimoto's thyroiditis. • Anti-Tg (Thyroglobulin Antibody) — directed against the scaffold protein of thyroid hormone production; less sensitive than anti-TPO but adds a small number of TPO-negative cases.
The two together cover > 95% of Hashimoto's patients and most patients with autoimmune hyperthyroidism (Graves').
Why it matters
Autoimmune thyroid disease is the commonest endocrine disorder in India after diabetes, affecting roughly 1 in 10 adults — overwhelmingly women. The classical presentation (fatigue, weight gain, hair loss, irregular periods, depression, infertility) is non-specific, so the diagnosis rests on TSH plus antibodies.
The ATAB panel is ordered when a TSH is borderline or raised, in unexplained subfertility (positive antibodies predict miscarriage and postpartum thyroiditis), when planning pregnancy, and to confirm the diagnosis of Hashimoto's before committing a patient to lifelong levothyroxine. A positive panel with a normal TSH still matters: about 5% of those people develop overt hypothyroidism each year.
How to prepare
No fasting required. Stop biotin / hair-skin-nail supplements for 48–72 hours before — high-dose biotin causes false readings in many thyroid assays. Continue thyroid hormone replacement as usual. Tell the lab if you have recently had iodine-contrast imaging.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Anti-TPO (IU/mL)[1] | < 35 IU/mL (assay-dependent) | Negative anti-TPO makes Hashimoto's much less likely, though does not rule it out completely (some patients are TPO-negative but anti-Tg positive). | Positive anti-TPO is highly suggestive of autoimmune thyroid disease. Very high titres (> 500 IU/mL) almost always indicate Hashimoto's thyroiditis. Lower titres can be seen in Graves' disease, postpartum thyroiditis or healthy people with a tendency to autoimmunity. |
| Anti-Thyroglobulin Antibody (Anti-Tg) (IU/mL)[1] | < 4.0 IU/mL (assay-dependent) | Negative anti-Tg with negative anti-TPO essentially rules out autoimmune thyroid disease. | Positive anti-Tg supports an autoimmune thyroid diagnosis. In thyroid cancer patients post-thyroidectomy, anti-Tg presence makes the thyroglobulin tumour marker unreliable, so anti-Tg trends are followed instead. |
ATAB panel — typical patterns
| Anti-TPO | Anti-Tg | TSH | Likely diagnosis |
|---|---|---|---|
| Positive (high) | Positive | Raised | Hashimoto's thyroiditis — start levothyroxine if overt |
| Positive (low) | Negative | Normal | Asymptomatic autoimmune tendency — monitor TSH yearly |
| Positive | Positive | Suppressed | Graves' disease (along with TRAb) or hashitoxicosis |
| Negative | Positive | Raised | TPO-negative Hashimoto's — uncommon but real |
| Negative | Negative | Raised | Non-autoimmune hypothyroidism (iodine deficiency, drugs, post-radiation) |
Frequently asked questions
Why do I need both antibodies tested?
Anti-TPO is the more sensitive single test, but adding anti-Tg catches a small number of cases that are TPO-negative. Together they cover more than 95% of autoimmune thyroid disease.
My antibodies are positive but my TSH is normal — do I need treatment?
Not usually. A positive antibody panel with a normal TSH (sometimes called "euthyroid autoimmune thyroiditis") indicates an autoimmune tendency. About 5% of these patients progress to overt hypothyroidism each year, so annual TSH monitoring is recommended.
I am planning pregnancy — should I get this panel done?
Yes, especially if you have any thyroid symptoms, a family history of thyroid disease, or previous miscarriage. Positive antibodies in pregnancy increase the risk of miscarriage, preterm delivery and postpartum thyroiditis, and many obstetricians treat sub-clinical hypothyroidism more aggressively when antibodies are positive.
Do antibody levels need to be repeated?
In established autoimmune disease, antibody levels do not change management — once positive, they stay positive in most patients. Repeat testing is mainly useful in thyroid cancer follow-up, not in routine Hashimoto's care.
Will levothyroxine bring the antibodies down?
Variably — many patients see a modest fall over years, but a substantial number remain antibody-positive lifelong. The aim of treatment is normal TSH, not zero antibodies.
Why are women so much more affected?
Autoimmune thyroid disease is 5–8× more common in women, with peaks around puberty, pregnancy and perimenopause. Oestrogen and X-chromosome immune genes are thought to be the main drivers, though the mechanism is not fully understood.
Can stress trigger thyroid antibodies?
Major life stress, severe illness and pregnancy can unmask or accelerate underlying autoimmune thyroid disease in genetically predisposed people, though stress is not the primary cause.
Related Hormones / Endocrine tests
Tests commonly ordered alongside Anti Thyroid Antibody (ATAB) Panel, or that help interpret an unexpected result.
Sources & references
- American Thyroid Association — Hypothyroidism Guideline · accessed 2026-05-30T00:00:00.000Z
- NIH MedlinePlus — Thyroid Antibodies Test · accessed 2026-05-30T00:00:00.000Z
- Indian Thyroid Society — Consensus · accessed 2026-05-30T00:00:00.000Z
- NCBI StatPearls — Hashimoto Thyroiditis · accessed 2026-05-30T00:00:00.000Z
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