Anti-thyroglobulin antibody (Thyroid autoantibody)
Sample for Anti-thyroglobulin antibody
- 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.
Precautions for Anti-thyroglobulin antibody
- Stop multivitamins and any other medication which will interfere with the result.
- Oral contraceptives may increase their value.
- Older people, especially women, may have antithyroglobulin antibodies.
Purpose of the test (Indications) for Anti-thyroglobulin antibody
- Useful for diagnosing thyroid diseases like Hashimoto’s thyroiditis and chronic lymphocytic thyroiditis.
- It differentiates Hashimoto’s thyroiditis and chronic lymphocytic thyroiditis in children.
- Several autoantibodies are organ-specific for the thyroid gland.
- The possible thyroid antigens giving rise to antibodies are:
- Hormone antigen.
- Thyroglobulin antigen.
- Thyroid microsomal antigen.
- Thyroid peroxidase antigen
- TSH-R antigen.
- Non-thyroglobulin colloidal antigen.
- Rarely can measure:
- TSH antigen.
- T4 and T3 antigens.
- Mostly anti-thyroglobulin and anti-thyroperoxidase are more frequently ordered by the physician.
- Anti-thyroglobulin antibodies are advised to evaluate:
- Thyroid malignancies.
- In Grave’s disease (autoimmune hyperthyroidism).
- In Hashimoto’s thyroiditis (autoimmune hypothyroidism).
- This is an autoimmune phenomenon. There is the formation of an autoantibody against thyroglobulin called the anti-thyroglobulin antibody.
- Thyroperoxidase is mostly used for autoimmune thyroid diseases.
- Thyroglobulin is also used as a tumor marker.
- 2/3 of the patients have preoperative raised levels of thyroglobulin.
- It 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 in the thyroid follicle can escape the follicle and become an antigen.
- Thyroperoxidase is located in the cytoplasm of the epithelial cells surrounding the follicles.
- Circulating thyroglobulin’s 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 blood circulation by the catabolism in the liver and recycling in the thyroid.
Autoantibodies against thyroglobulin:
- These autoantibody reacts with thyroglobulin and leads to thyroid destruction and inflammation.
- Anti-thyroglobulin antibodies exist in 10% of the normal population and >20% in thyroid cancer.
- Anti-thyroid globulin antibodies can also be used to monitor residual disease (tumor recurrence).
- Increased levels of Anti-thyroid globulin antibodies may suggest a recurrence of the tumor.
- An increase in the anti-thyroglobulin antibody indicates antigenic stimulation, suggesting recurrence.
- If these antibodies are present in the mother, there is an increased risk of hypo or hyperthyroidism in the fetus and the newborn.
Thyroid autoantibodies and thyroid diseases:
|Type of autoantibody||In normal population||Autoimmune hypothyroidism||Grave’s disease|
|Antithyroglobulin Ab||3%||35% to 65%||12% to 30%|
|Anti-TSH receptor Ab||1% to 2%||6% to 60%||70% to 100%|
|Thyroid peroxidase Ab||10% to 15%||80% to 99%||45% to 80%|
- Other thyroid autoantibodies form against microcosms and are called anti-microsomal antibodies; these are also advised to diagnose thyroid diseases.
- The most commonly advised antibodies are thyroid peroxidase autoantibodies.
- 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 their level of thyroglobulin.
- Anti-thyroglobulin antibodies can also be used to monitor the residual disease or to find the recurrence.
- An increased level of Anti-Thyroglobulin indicates the recurrence of the disease (cancer).
Table showing % of the antithyroglobulin antibodies in various diseases.
When to ask for an antithyroglobulin antibody test (Clinical presentation):
- 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.
The normal level of antithyroglobulin antibody:
- Negative = Titer = <1:100
- A small normal population may have an antithyroglobulin antibody.
- 5% to 10% normal population may show low titer.
- 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 thyroid disease.
- This low titer is common in women and increasing age.
- In some cases, this antibody production may be confined to the lymphocytes within the thyroid, resulting in negative serum tests.
How to measure anti-thyroglobulin antibodies:
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 Anti-thyroglobulin antibody level is seen in the following:
- 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.
- Atrophic thyroiditis.
- Thyroid cancer
- Pernicious anemia.
- Sjogren’s syndrome.
- Lupus erythematosus.
- Table showing various thyroid diseases and autoantibodies:
|Disease||Anti-thyroglobulin antibody||Anti-microsomal antibody||
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.
Questions and answers: