Antithyroglobulin: What is it? History, Types and Everything About the Antibody Test

It is an antibody directed against thyroglobulin which is a key protein in the thyroid gland, essential for the production of thyroid hormones (thyroxine and triiodothyronine).

Antithyoglobulin antibodies can damage the thyroid gland and affect its function.

The anti-thyroglobulin antibody test in the blood is useful in the diagnosis of some thyroid disorders and other conditions.

Conditions in which anti-thyroglobulin antibodies can be created include:

Antithyoglobulin antibodies are also called antithyroid antibodies.

History

In 1912 Hashimoto described hypothyroidism and goiter associated with thyroid lymphoid infiltration.

In 1956 the anti-Tg antibody was detected in similar cases, elucidating the autoimmune cause of these characteristics.

Later in the same year, TSH receptor activating antibodies were discovered.

Thyroid microsomal antibodies were discovered in 1964, which were subsequently termed anti-TPO antibodies due to the identification of their autoantigen.

Types

Antithyroid antibodies can be subdivided into groups according to their target antigen.

Anticuerpos anti-TPO:

Anti-thyroid peroxidase (anti-TPO) antibodies are specific for the autoantigen TPO, a glycoprotein that catalyzes the oxidation of iodine and the tyrosyl thyroglobulin iodination reactions in the thyroid gland.

Anti-TPO antibodies are the most common antithyroid autoantibody, present in approximately 90% of Hashimoto’s thyroiditis, 75% of Graves’ disease and 10-20% of nodular goiter or thyroid carcinoma.

In addition, between 10 and 15% of normal people may have high levels of anti-TPO antibodies.

High serum antibodies are found in chronic active autoimmune thyroiditis.

Therefore, an antibody meter can be used to assess the activity of the disease in patients who have developed such antibodies.

Most anti-TPO antibodies are produced by infiltrating lymphocytes of the thyroid, with minor contributions of the lymph nodes and bone marrow.

They cause damage to thyroid cells by complement activation and antibody-dependent cellular cytotoxicity.

However, it is not believed that anti-TPO antibodies contribute to the destruction of the thyroid.

TSH receptor antibodies:

The thyrotropin receptor (TSH receptor) is the antigen for TSH receptor antibodies (TRAbs).

It is a receptor coupled to seven transmembrane G proteins that is involved in the signaling of thyroid hormone.

The TRAb are grouped according to their effects on the signaling of the receiver; activate antibodies (associated with hyperthyroidism), block antibodies (associated with thyroiditis) and neutral antibodies (without effect on the receptor).

TRAb are present in 70-100% of Graves’ disease (85-100% for activating antibodies and 75-96% for blocking antibodies) and 1-2% of normal individuals.

The activation of TRAbs is characteristic of Graves’ disease (autoimmune hyperthyroidism).

The TPO antibody is more easily measured than the TSH receptor antibody, and is therefore often used as a surrogate in the diagnosis of Graves’ disease.

These antibodies activate adenylate cyclase by binding to the TSH receptor.

This causes the production of thyroid hormones and the subsequent growth and vascularization of the thyroid.

TRAb are also useful in the diagnosis of Graves’ ophthalmopathy.

Although the exact mechanism of how TRAbs induce Graves’ ophthalmopathy is unknown, it is likely that antibodies bind to TSH receptors in retro-orbital tissues, which causes lymphocyte infiltration.

This inflammatory response leads to the production of cytokines, which cause fibroblasts to produce glycosaminoglycans, leading to ophthalmopathy.

Blocking TRAbs (also known as thyrotropin binding inhibitor immunoglobulins (TBII)) competitively blocks the activity of TSH in the receptor.

This can cause hypothyroidism by reducing the thyrotropic effects of TSH.

They are found in Hashimoto’s thyroiditis and Graves’ disease and may be the cause of the fluctuation of thyroid function in the latter.

During the treatment of Graves’ disease, they can also become the predominant antibody, which can cause hypothyroidism.

The clinical and physiological relevance of neutral antibodies remains unclear.

However, they may be involved in prolonging the half-life of the TSH receptor.

Thyroglobulin antibodies:

Thyroglobulin antibodies are specific for thyroglobulin, a matrix protein involved in the production of thyroid hormone.

They are found in 70% of Hashimoto’s thyroiditis, 60% of idiopathic hypothyroidism, 30% of Graves’ disease, a small proportion of thyroid carcinoma and in 3% of normal individuals.

Anti-TPO antibodies are present in 99% of the cases in which thyroglobulin antibodies exist, however, only 35% of positive cases of anti-TPO antibodies also show to have thyroglobulin antibodies.

Anti-Na + / I- symporter:

Anti-Na + / I-symporter antibodies are a more recent discovery of possible thyroid autoantibodies and their role in thyroid disease remains uncertain.

They are present in approximately 20% of Graves’ disease and 24% of Hashimoto’s thyroiditis.

Anti-thyroglobulin antibody test

The Antithyroglobulin Antibody test is performed to measure the antibodies known as thyroglobulin, a protein found in the thyroid cells of the thyroid gland.

The thyroid gland is a small butterfly-shaped gland located in the lower front of the neck and responsible for producing the hormones T3 and T4.

These two hormones help control your metabolism that is used to provide energy to your body.

This test helps diagnose thyroid problems, including Hashimoto’s thyroiditis and autoimmune thyroid disease.

Your doctor may order an antithyroglobulin test if you have symptoms of a thyroid disorder, such as:

  • Fatigue.
  • Unexplained weight gain.
  • Constipation .
  • Dry Skin.

You can also order it if you develop a goiter, a condition that occurs when the thyroid gland enlarges.

preparation:

In general, you will be asked to stop eating and drinking several hours before the test, usually during the night.

Your doctor will want to look at your condition and if you are taking any medication, you may be asked to stop taking it, as this may hinder the results of the test.

Do not stop any medication without the consent of your doctor.

Other points to remember are:

  • Wear a shirt or a short-sleeved shirt to make it easier, especially the technician, who can draw blood easily.
  • Twelve hours before you have to have a blood test, do not take any dietary supplement that contains vitamin B7, biotin or multivitamins, unless your doctor allows it.

Process:

A health technician will first cleanse the skin using an antiseptic and then tie a tourniquet or band on the upper arm and apply pressure that will cause swelling in the arm as blood begins to accumulate.

Then, the technician will take a syringe that he will then insert into his veins. It is usually on the back of the hand or inside the elbow area.

Then, the technician will extract the necessary amount of blood that is needed for the test. When removing the syringe, the technician will apply a bandage to the area where the syringe is removed to stop bleeding.

This whole process takes only a few minutes.

Purpose:

The main reason for this test is to check if you have a problem related to the thyroid.

If anti-thyroglobulin antibodies are found, this is considered to be damage to the thyroid gland caused by your immune system.

This test is also important for patients who have overcome thyroid cancer.

By measuring thyroglobulin antibody levels, the technologist can confirm if there is any possibility of recurrence of thyroid cancer possibilities.

The other diseases that can be verified with the anti-thyroglobulin antibody test are: postpartum thyroiditis, Graves disease and neonatal hypothyroidism.

Risks:

For most people, this test involves minimal risks.

They are common to all routine blood tests.

For example, you may experience discomfort when your blood is drawn.

You may develop some pain, palpitations or bruising at the puncture site.

If the nurse or technician has trouble drawing a sample of your blood, you may need to inject the needle several times.

Other risks include:

  • Stunning: with subsequent fainting.
  • Excessive bleeding: at the puncture site.
  • Accumulation of blood under your skin:  known as a bruise.
  • Development of an infection: where the skin breaks with the needle.
  • Inflammation of your vein:  known as phlebitis.

Results:

The normal results for this test are “negative”.

If you receive negative results, that means no anti-thyroglobulin antibodies were found in your blood sample.

If you have small amounts in your blood, it can be a sign of certain health problems, such as:

If you have high levels of anti-thyroglobulin antibodies in the blood, it can be a sign of a serious autoimmune disorder, such as Graves’ disease or Hashimoto’s thyroiditis.

In some cases, you may have anti-thyroglobulin antibodies in your blood without specific complications.

If the test is positive for these antibodies, and your doctor can not identify an underlying cause, you may be able to control it for incipient health problems.

Your doctor can help you understand the results of your test. Your recommended follow-up steps will depend on the specific diagnosis. For example, they may recommend additional tests or treatment options.

Ask your doctor for more information about the results of the test, the condition, and the next steps.