Anti-thyroglobulin antibody

What sample is needed for the Anti-thyroglobulin antibody?

1. Collect 3 to 5 ml of blood and prepare serum.
2. Keep the serum frozen if the test is not done on the same day.
3. The fasting sample is preferred.

What Precautions will you take for Anti-thyroglobulin antibody?

1. Stop multivitamins and any other medication that will interfere with the result.
2. Oral contraceptives may increase their value.
3. Older people, especially women, may have antithyroglobulin antibodies.

What are the Indications for Anti-thyroglobulin antibody?

1. Useful for diagnosing thyroid diseases like Hashimoto’s thyroiditis and chronic lymphocytic thyroiditis.
2. It differentiates Hashimoto’s thyroiditis and chronic lymphocytic thyroiditis in children.
3. Hypothyroidism.
4. Hyperthyroidism.
5. Thyroid malignancies.
6. In Graves’ disease (autoimmune hyperthyroidism).
7. In Hashimoto’s thyroiditis (autoimmune hypothyroidism)

What are the Thyroid antigens?

1. Several autoantibodies are organ-specific for the thyroid gland.
2. The possible thyroid antigens giving rise to antibodies are:
   1.  Hormone antigen.
   2. Thyroglobulin antigen.
   3. Thyroid microsomal antigen.
   4. Thyroid peroxidase antigen
   5. TSH-R antigen.
   6. Non-thyroglobulin colloidal antigen.
   7. Rarely can we measure:
      1. TSH antigen.
      2. T4 and T3 antigens.

3. The physician most frequently orders anti-thyroglobulin and anti-thyroperoxidase.
4. Anti-thyroglobulin antibodies are advised to evaluate:
   1. Hypothyroidism.
   2. Hyperthyroidism.
   3. Thyroid malignancies.
   4. In Graves’ disease (autoimmune hyperthyroidism).
   5. In Hashimoto’s thyroiditis (autoimmune hypothyroidism).
5. This is an autoimmune phenomenon. An autoantibody against thyroglobulin is formed, called the anti-thyroglobulin antibody.
   1. Thyroperoxidase is mostly used for autoimmune thyroid diseases.

How will you discuss the Thyroglobulin?

1. Thyroglobulin is also used as a tumor marker.
   1. 2/3 of the patients have preoperative raised levels of thyroglobulin.
2. It is a 660 kD glycoprotein, a dimeric protein produced by the follicular cells, and is used entirely in the gland.
3. This is the precursor of the thyroid hormone (thyroxine and triiodothyronine).
   1. Thyroglobulin combines with T4 by oxidation through peptide linkage.
4. Thyroglobulin is synthesized in the follicular cells.
   1. There is a high concentration of thyroglobulin in the colloid inside the thyroid follicle.
   2. It enters the lumen of the follicle by the process of exocytosis.
   3. Circulating thyroglobulin’s half-life is about 65 hours.
   4. It takes nearly a month before thyroglobulin becomes undetectable after the total thyroidectomy.
   5. Thyroglobulin is cleared from blood circulation by catabolism in the liver and recycling in the thyroid.
   6. The thyroglobulin in the thyroid follicle can escape the follicle and become an antigen.
5. Thyroperoxidase is located in the cytoplasm of the epithelial cells surrounding the follicles

What are the functions of autoantibodies against thyroglobulin?

1. Anti-thyroglobulin antibodies exist in 10% of the normal population and >20% in thyroid cancer.
   1. These autoantibodies react with thyroglobulin and lead to thyroid destruction and inflammation.
   2. Anti-thyroid globulin antibodies can also be used to monitor residual disease (tumor recurrence).
   3. Increased levels of  Anti-thyroid globulin antibodies may suggest a recurrence of the tumor.
   4. An increase in the anti-thyroglobulin antibody indicates antigenic stimulation, suggesting recurrence.
   5. If these antibodies are present in the mother, there is an increased risk of hypo- or hyperthyroidism in the fetus and the newborn.

What are other thyroid autoantibodies?

1. Other thyroid autoantibodies form against microcosms and are called anti-microsomal antibodies; these are also used to diagnose thyroid diseases.
2. The most commonly advised antibodies are thyroid peroxidase autoantibodies.
3. Hashimoto’s thyroiditis is characterized by a high titer of anti-thyroglobulin and anti-microsomal antibodies, a level of >1:400.
4. Thyroglobulin can be used as a tumor marker.
   1. 2/3 of the patients with thyroid cancer have raised levels of thyroglobulin.
   2. Anti-thyroglobulin antibodies can also be used to monitor the residual disease or to detect recurrence.
   3. An increased level of Anti-Thyroglobulin indicates the recurrence of the disease (cancer).

What are the antithyroglobulin antibodies in various diseases?

 When should you ask for an antithyroglobulin antibody test?

1. If the patient has the following symptoms:
   1. If there is weight gain without any explanation.
   2. Patients have a history of fatigue.
   3. History of constipation.
   4. In the case of dry skin.

What is the normal level of antithyroglobulin antibody?

Source 2

• Negative = Titer = <1:100
  • A small normal population may have an antithyroglobulin antibody.
  • 5% to 10% of the normal population may show a low titer.

Source 4

1. Anti-thyroglobulin = <1:100 (by haemagglutination).
2. Negative by ELIZA.
3. Negative by chemiluminescence.
   1. 10% of the population have low titer positive for the antibody without any symptoms of thyroid disease.
   2. This low titer is common in women and with increasing age.
4. 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, such as:

1. Passive hemagglutination.
2. The agar gel diffusion precipitation method.
3. Immunofluorescence of the tissue biopsy.
4. Enzyme-linked Immunoabsorbent assay (ELIZA).
5. Chemilucent-based immunoassay.

What are the causes of increased Anti-thyroglobulin antibody levels?

1. Chronic thyroiditis, like Hashimoto thyroiditis, in adults.
   1. The titer is high,>1:25,000, strongly suggesting Hashimoto’s disease.
   2. This autoantibody is positive in 50% of the cases of Hashimoto’s thyroiditis.
   3. The normal level of thyroglobulin antibody does not rule out Hashimoto’s disease.
2. Chronic lymphocytic thyroiditis in children and young adults.
3. Graves’ disease.
4. Hypothyroidism.
5. Atrophic thyroiditis.
6. Thyroid cancer
7. Thyrotoxicosis.
8. Myxedema.
9. Pernicious anemia.
10. Sjögren’s syndrome.
11. Lupus erythematosus.

How will you describe various thyroid diseases and autoantibodies?

• LATS consists of two antibodies:
  • TSI = Thyroid-stimulating immunoglobulin.
  • TSH-R antibody = Thyroid hormone receptor antibody.

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