Thyroid Stimulating Immunoglobulin Test in the Diagnosis of Thyroid Disease

Thyroid stimulating immunoglobulin test is a modern test

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Thyroid stimulating immunoglobulin (TSI) is an antibody produced in high titers when the thyroid gland is defective. The exact amount of this antibody is estimated in your blood serum using the TSI test. TSI test is a serological test based on antigen-antibody reaction.

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When is Thyroid Stimulating Immunoglobulin Test Necessary?

Your doctor recommends the TSI test when you show signs that are consistent with those of a defective thyroid gland.

The signs and symptoms indicate that there could be overstimulation of your thyroid gland (Hyperthyroidism) making it produce abnormally high amounts of triiodothyronine (T3) and thyroxine (T4).

The thyroid hormones T3 and T4 are elevated due to Thyroid Stimulating Immunoglobulin (Deposit Photos) illustrated in 3D here

The amount of these hormones alongside thyroid stimulating hormone (TSH) could also be measured to complement the TSI test. This is to ensure a better interpretation of the stage of your thyroid gland disease.

Signs and Symptoms that Inform TSI Test

Most of the patients will show similar signs and symptoms. However, there might be slight differences among patients. Patients will show the manifestation of hyperthyroidism.

This could be an emergency that can fatal especially if the flare-up is too sudden. Here you will have abnormally high amounts of circulating thyroid hormones. This is also referred to as thyroid storm or thyrotoxicosis.

The most common clinical presentation is bulging out of the eyes, and the inability to align your eyes (Both) in the same direction. Others include palpitations, restlessness, fatigue, tremors, and general weight loss.

Preparation for Thyroid Stimulating Immunoglobulin Test

The preparation for the TSI test is very simple. You simply avail yourself to the phlebotomist. The phlebotomist will then take a small blood sample from you.

I am quite sure that this would not be the first time you are being bled from your vein (venipuncture) in the upper arm, is it?

Therefore, you need to relax as the discomfort of being pricked using a needle would not be anything more than the usual little discomfort. It hardly lasts for 3 minutes.

Performing Thyroid Stimulating Immunoglobulin Test

The phlebotomist takes the blood sample and conveys it to the laboratory technologists/technicians/scientists or whoever is responsible. The laboratory scientist will first spin your blood in a centrifuge to obtain the serum (the liquid part of the blood) also known as plasma.

However, there is a small difference between serum and plasma. This test can use either of the two. The laboratory may use any serological test to detect these autoantibodies i.e. the TSI. In the USA and other jurisdictions, the laboratory may procure a complete thyroid panel for this test among other tests. The most commonly used techniques include ELISA, and Flow cytometry

TSI Test and Interpretation of the Results


Interpretation should strictly be left to your doctor as some cases with low circulation TSI yet have early signs of Grave’s disease. Therefore, these are not the kind of tests that you want to gamble with interpretation lest you assume that you aren’t sick yet you are.

On the other hand, you may misinterpret it as having a serious level of the disease and get depressed while that may not be the case. Please let your doctor play their part effectively, right?

Normal Results

The normal values of the test will be less than 130% basal activity. The results may also be expressed as TSI index 1.3. If the test results are normal, your doctor will request additional tests to uncover the cause of your signs and symptoms.

Abnormal Results

Abnormal results of the TSI test especially when consistent with elevated concentrations of TSH, T3, and T4 mean you are unwell. The abnormal results may indicate the possibility of the following:

Grave’s Disease

This is an autoimmune disease in which there is overstimulation of the thyroid gland and consequently the overproduction of TSH, T3, and T4 hormones. There are autoantibodies in your blood that coordinate the destruction of your thyroid by the immune system.

Female doctor examining a man with thyroid disease due to thyroid stimulating immunoglobulin (Deposit Photos)

The TSI molecularly engages the thyroid hormone the same way it would be stimulated by TSH further leading to hyperthyroidism. Grave’s disease can lead to other secondary diseases like diabetes mellitus type 1. A positive TSI test is nearly always indicative of Grave’s disease. Our friends at the have a greatly subsidized test kit for TSI that you can order hassle-free online.

Transient Neonatal Grave’s Disease

Pregnant mothers may be subjected to the TSI test, particularly in the 3rd semester. This may be necessitated by signs of hyperthyroidism. The other group of women who may be required to undergo this test is those with a history of hyperthyroidism.

The reason for this test during pregnancy is TSI antibodies and IgG type. We know that IgG can cross the placenta and so a possibility of crossing to your unborn baby. You don’t want to give birth to a baby with hyperthyroidism. If this happens your newborn will suffer from neonatal Grave’s disease.

Transient neonatal Grave’s disease is a milder form of the adults’ Graves disease. There is no cause to worry because this condition is treatable. Shortly after birth, the amount of circulation TSI in your baby’s system can be reduced.

This will consequently, reduce signs of hyperthyroidism. In the USA alone, it is estimated that 2 children out of every 1000 unborn children suffer hyperthyroidism.  This number may seem small, but it would be great to ensure that these children live a normal life.

Hashimoto’s Thyroiditis – In this disease there is massive inflammation of the thyroid gland and insufficient production of the thyroid hormones. The gland cells become necrotic and hence unable to function optimally.


This is not an autoimmune disease nor a disease that causes the production of autoantibodies. In goiter, the thyroid gland is enlarged, and the test is different from the TSI test. However, the TSI test can be employed as a complementary test in the diagnosis of toxic multinodular goiter.

Sometimes, the TSI test is done to either complement other types of thyroid tests or to supplement the other tests when for some reason you cannot take the tests. The other tests include biopsy, thyroid blood test, thyroid uptake and scan, physical examination, ultrasound, CT scans, and magnetic resonance imaging.

Risks Associated with TSI Test

There are no major risks associated with the TSI test. However, there may be a few issues related to venipuncture when providing a blood sample to the laboratory.

Some people may bleed for longer than others, some may develop a hematoma (blood clot under the skin). Hematoma develops when the needle pricks tissues instead of getting into the lumen of the blood vein. Infection may develop at the wound site but this is quite rare.


The thyroid stimulating immunoglobulin test is an important test in the diagnosis of thyroid disease. It is minimally invasive and so no one should fear the test. It is the test that helps in the diagnosis of Grave’s disease and sometimes thyroiditis.

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