Anti-thyroglobulin antibody (Thyroid auto-antibody, Thyroglobulin antibody)

Sample
- Collect 3 to 5 ml of blood and prepare serum.
- Keep the serum frozen if the test is not done on the same day.
- The fasting sample is preferred.
Precaution
- Stop multivitamins and any other medication which will interfere with the result.
- Oral contraceptive may increase the value
Purpose of the test
- useful for the diagnosis of thyroid diseases like Hashimoto’s thyroiditis and chronic lymphocytic thyroiditis.
- It differentiates Hashimoto’s thyroiditis and chronic lymphocytic thyroiditis.
Pathophysiology
- There are several autoantibodies that are organ-specific for the thyroid gland.
- The possible thyroid antigens are:
- Hormone antigen.
- Thyroglobulin antigen.
- Thyroid microsomal antigen.
- TSH-R antigen.
- Non-thyroglobulin colloidal antigen.
- Mostly anti-thyroglobulin and anti-thyroperoxidase are more frequently ordered by the physician.
- These are advised to evaluate:
- Hypothyroidism.
- Hyperthyroidism.
- Thyroid malignancies.
- In Grave’s disease (autoimmune hyperthyroidism).
- In Hashimoto’s thyroiditis (autoimmune hypothyroidism).
- These are advised to evaluate:
- This is an autoimmune phenomenon. There is the formation of autoantibody against thyroglobulin called the anti-thyroglobulin antibody.
- Thyroperoxidase mostly used for autoimmune thyroid diseases.
- Thyroglobulin is a glycoprotein, 660 kD, a dimeric protein produced by the follicular cells, and is used entirely in the gland.
- This is the precursor of the thyroid hormone (thyroxine and triiodothyronine).
- Thyroglobulin combines with T4 by oxidation through peptide linkage.
- Thyroglobulin is synthesized in the follicular cells.
- There is a high concentration of thyroglobulin in the colloid inside the thyroid follicle.
- It enters the lumen of the follicle by the process of exocytosis.
- The thyroglobulin located in the thyroid follicle can escape the follicle and becomes antigen.
- Thyroperoxidase located on the cytoplasm of the epithelial cells surrounding the follicles.
- Circulating thyroglobulin half-life is about 65 hours.
- It takes nearly a month before thyroglobulin becomes undetectable after the total thyroidectomy.
- Thyroglobulin is a demo cleared from the blood circulation by the catabolism in the liver and recycling in the thyroid.
- This is the precursor of the thyroid hormone (thyroxine and triiodothyronine).
- These autoantibody reacts with the thyroglobulin and leads to thyroid destruction and inflammation.
- Anti-thyroglobulin antibodies are present in 10% of the normal population and >20% in thyroid cancer.
- An increase in the anti-thyroglobulin antibody is indicative of antigenic stimulation, suggesting recurrence.
- If these antibodies are present in the mother then there is an increased risk of hypo or hyperthyroidism in the fetus and the newborn.
- Other thyroid autoantibodies form against microcosms and called an anti-microsomal antibody, these are also advised.
- A high titer of anti-thyroglobulin and anti-microsomal antibodies level of >1:400 is found in Hashimoto’s thyroiditis.
- Thyroglobulin can be used as a tumor marker.
- 2/3 of the patient with thyroid cancer have raised the level of thyroglobulin.
- Antu-thyroglobulin antibodies can also be used to monitor the residual the disease or to find the recurrence.
- Raised level of the Anti-Tg indicates the recurrence of the disease (cancer).
- Thyroglobulin can be used as a tumor marker.
Table showing % of the antithyroglobulin antibodies in various diseases.
Diseases | Antithyroglobulin Ab % |
---|---|
Normal male | 2 |
Normal female | 10 |
Hashimoto’s Thyroiditis | 70 |
Myxedema | 55 |
Grave’s disease | 55 |
Nontoxic goiter | 5 to 50 |
Thyroid cancer | 20 |
Indication for antithyroglobulin antibody test:
- If the patient has the following symptoms:
- If there is weight gain without any explanation.
- Patients have a history of fatigue.
- History of constipation.
- In the case of dry skin.
Normal
Source 2
- Titer = <1:100
- A small normal population may have an antithyroglobulin antibody.
- 5 to 10% normal population may show low titer.
Source 4
- Anti-thyroglobulin = <1:100 (by haemagglutination).
- Negative by ELIZA.
- Negative by chemiluminescence.
- 10% of the population have low titer positive for the antibody without any symptoms of the thyroid disease.
- This low titer is common in women and in the increasing age.
- 10% of the population have low titer positive for the antibody without any symptoms of the thyroid disease.
- In some cases this antibody production may be confined to the lymphocytes within the thyroid, resulting in negative serum tests.
Lab diagnosis of anti-thyroglobulin antibody:
There are different methods to detect anti-thyroglobulin antibodies like:
- Passive hemagglutination.
- The agar gel diffusion precipitation method.
- Immunofluorescence of the tissue biopsy.
- Enzyme-linked Immunoabsorbent assay (ELIZA).
- Chemilucent based immunoassay.
The increased level is seen in:
- Chronic thyroiditis like Hashimoto thyroiditis in the adult.
- The titer is high >1:25,000 is strongly suggestive of Hashimoto’s disease.
- This autoantibody is positive in 50% of the cases of Hashimoto’s thyroiditis.
- The normal level of thyroglobulin antibody does not rule out Hashimoto’s disease.
- Chronic lymphocytic thyroiditis in children and young adults.
- Graves’ disease.
- Hypothyroidism.
- atrophic thyroiditis.
- Table showing various thyroid diseases and autoantibodies:
Disease | Anti-thyroglobulin antibody | Anti-microsomal antibody |
Antithyroperoxidase antibody |
Long-acting thyroid stimulating antibody (LATS) |
Grave’s disease | positive 30% | positive 60 to 80% | positive >70% | positive 100% |
Hashimoto’s thyroiditis | positive 70 to 90% | positive 80% | positive 100% | negative |
Lymphocytic thyroiditis | positive 30 to 50% | positive 50% | positive | negative |
Thyroid carcinoma | positive 20 to 50% | positive 15% | negative | |
Normal person | positive low titer | positive 5 to 10% |
- LATS consists of two antibodies:
- TSI = Thyroid stimulating immunoglobulin.
- TSH-R antibody = Thyroid hormone receptor antibody.