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Thyroid

TSI (Thyroid Stimulating Immunoglobulin)

TSI antibodies are associated with Graves' disease and may influence thyroid function. In women, thyroid health can be closely linked to menstrual cycle regularity and hormonal balance. Discuss any thyroid concerns with your healthcare provider for guidance.

Doctor's Assessment Included

Reference Ranges

No established reference range

There is no generally accepted reference value for TSI (TSH-receptor antibodies). The NVKC states that no general normal values are available and that reference values depend on the assay used. The Dutch thyroid guideline states that an absolute cut-off cannot be formulated, because the available assays are not standardised against one another; it therefore uses a threshold of three times the performing laboratory's own upper limit. For TSI it is not only the cut-off that differs by method but the unit itself: laboratories report this test in international units per litre, as a percentage of stimulation relative to a reference, or simply as positive or negative. Your result is therefore always assessed against both the unit and the cut-off of the laboratory that ran the test.

Reference ranges may vary between laboratories. When you order a test, a BIG-registered doctor assesses your personal results in context. For treatment decisions, discuss your results with your GP.

What It Measures

This test measures thyroid-stimulating immunoglobulin antibodies in your blood. These antibodies may bind to TSH receptors on the thyroid gland, potentially stimulating excess thyroid hormone production. TSI is considered a key diagnostic indicator that healthcare providers use when evaluating suspected Graves' disease.

Why It Matters

Thyroid autoimmunity detected through TSI testing may be particularly relevant for women, as it can potentially affect menstrual cycles, fertility, and pregnancy outcomes. Your healthcare provider can advise on monitoring and management strategies tailored to your reproductive health goals.

When to Test

Healthcare providers may recommend TSI testing when hyperthyroidism is suspected, particularly if symptoms such as unexplained weight loss, rapid heartbeat, or eye changes are present. It may also be used to monitor Graves' disease treatment progress or during pregnancy when thyroid antibodies could affect the baby.

Symptoms

Low Levels

Low or undetectable TSI levels are generally considered normal and typically do not cause symptoms. The absence of these antibodies may suggest that Graves' disease is less likely as a cause of any thyroid-related symptoms you may be experiencing. Consult your healthcare provider for a comprehensive evaluation.

High Levels

Some people with elevated TSI may experience symptoms associated with hyperthyroidism, such as unexplained weight loss, increased heart rate, tremors, heat intolerance, anxiety, or eye protrusion. These symptoms may vary in severity. Your healthcare provider can recommend appropriate next steps based on your individual situation.

Lifestyle Tips

While lifestyle changes alone may not directly lower TSI levels, some people find that stress management techniques, adequate sleep, and a balanced diet may support overall thyroid health. Avoiding excessive iodine intake is sometimes recommended. Always follow your healthcare provider's guidance regarding treatment and lifestyle modifications.

Frequently Asked Questions

What is the difference between TSI and TSH?
TSH is a hormone produced by the pituitary gland that regulates thyroid function. TSI is an antibody produced by the immune system that may mimic TSH, potentially causing the thyroid to produce excess hormones. Your healthcare provider can explain how these markers relate to your health.
Can TSI levels change over time?
Yes, TSI levels may fluctuate depending on disease activity and treatment. Some people may see levels decrease with successful treatment of Graves' disease. Regular monitoring, as recommended by your healthcare provider, can help track these changes.
Is fasting required before a TSI test?
Fasting is generally not required for a TSI blood test. However, it is advisable to follow any specific preparation instructions provided by your healthcare provider or testing facility to ensure accurate results.

Tests with related values

These panels measure values from the same category as this marker.

Fertility & Pregnancy

IVF Blood Test Complete (Women)

Everything in the IVF panel plus full thyroid, preconception nutrients, progesterone and CMV immunity.

TSH (Thyroid Stimulating Hormone) Prolactin AMH (Anti-Müllerian Hormone) Estradiol (E2) FSH (Follicle Stimulating Hormone) LH (Luteinizing Hormone) Free T4 (Thyroxine) Folate (Folic Acid) Vitamin B12 Ferritin Progesterone Vitamin D (25-OH) Chlamydia IgG HIV 1/2 Antibody + p24 Antigen Syphilis Screening Blood Type + Rh TPO Antibodies CMV IgG Hepatitis B Core Antibody Hepatitis B Surface Antigen Hepatitis C Antibody Rubella IgG Toxoplasmosis IgG Varicella Zoster D-Dimer Basic Blood Count
€495,-

TSI (Thyroid Stimulating Immunoglobulin)

€81,-