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Thyroid

TSI Test: Thyroid-Stimulating Immunoglobulin

TSI antibodies may indicate Graves' disease, which can lead to hyperthyroidism. For active individuals, an overactive thyroid may affect metabolism, heart rate, and recovery. Understanding your TSI status can be part of a comprehensive approach to performance health.

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.

TSI (Thyroid Stimulating Immunoglobulin): what this test 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.

TSI (Thyroid Stimulating Immunoglobulin): why this value matters

Active individuals with undetected Graves' disease may experience unexplained performance decline, elevated resting heart rate, or difficulty with recovery. TSI testing may help identify the underlying cause, allowing your healthcare provider to recommend strategies that support your training goals.

TSI (Thyroid Stimulating Immunoglobulin): when is testing worthwhile?

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.

TSI (Thyroid Stimulating Immunoglobulin): symptoms of a high or low value

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.

TSI (Thyroid Stimulating Immunoglobulin): lifestyle and this value

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.

TSI (Thyroid Stimulating Immunoglobulin): 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.

Whoop

Whoop Women's Health

A 53-biomarker women's health panel inspired by the WHOOP Women's Health Panel — fertility, cycle and thyroid hormones plus a complete metabolic and nutrient base.

Complete Blood Count (CBC) Leukocyte Differential ALP (Alkaline Phosphatase) ALT (Alanine Aminotransferase) AST (Aspartate Aminotransferase) Albumin Total Protein Bilirubin (Total) ApoB (Apolipoprotein B) Total Cholesterol LDL Cholesterol HDL Cholesterol Triglycerides Lipoprotein(a) Urea (BUN) Creatinine eGFR (Estimated Glomerular Filtration Rate) Calcium Bicarbonate Chloride Sodium Potassium Magnesium Cortisol DHEA-S Estradiol (E2) FSH (Follicle Stimulating Hormone) LH (Luteinizing Hormone) SHBG (Sex Hormone Binding Globulin) Total Testosterone Free Testosterone TSH (Thyroid Stimulating Hormone) Glucose (Fasting) HbA1c (Glycated Hemoglobin) Insulin (Fasting) HOMA-IR CRP (C-Reactive Protein) Homocysteine Ferritin Iron (Serum) Transferrin Transferrin Saturation Vitamin D (25-OH) AMH (Anti-Müllerian Hormone) Progesterone Prolactin TPO Antibodies Free T3 (Triiodothyronine) Free T4 (Thyroxine) Leptin Vitamin B12 Folate (Folic Acid) Phosphorus
€709,-
Complete Health

360 Health

Broad health panel: hormones, thyroid, vitamins, lipids, liver, kidney, and blood count.

HbA1c (Glycated Hemoglobin) TSH (Thyroid Stimulating Hormone) Triglycerides Urea (BUN) Creatinine eGFR (Estimated Glomerular Filtration Rate) Free T4 (Thyroxine) LDL Cholesterol Liver Function Test (LFT) SHBG (Sex Hormone Binding Globulin) Vitamin B12 Vitamin D (25-OH) Total Testosterone Free T3 (Triiodothyronine) Ferritin HDL Cholesterol Albumin Total Cholesterol Basic Blood Count
€346,-
Whoop

Whoop Metabolic Health

A 51-biomarker metabolic panel inspired by the WHOOP Metabolic Health Panel — blood sugar regulation, insulin, thyroid, liver and the mineral cofactors behind your metabolism.

Complete Blood Count (CBC) Leukocyte Differential ALP (Alkaline Phosphatase) ALT (Alanine Aminotransferase) AST (Aspartate Aminotransferase) Albumin Total Protein Bilirubin (Total) ApoB (Apolipoprotein B) Total Cholesterol LDL Cholesterol HDL Cholesterol Triglycerides Lipoprotein(a) Urea (BUN) Creatinine eGFR (Estimated Glomerular Filtration Rate) Calcium Bicarbonate Chloride Sodium Potassium Magnesium Cortisol DHEA-S Estradiol (E2) FSH (Follicle Stimulating Hormone) LH (Luteinizing Hormone) SHBG (Sex Hormone Binding Globulin) Total Testosterone Free Testosterone TSH (Thyroid Stimulating Hormone) Glucose (Fasting) HbA1c (Glycated Hemoglobin) Insulin (Fasting) HOMA-IR CRP (C-Reactive Protein) Homocysteine Ferritin Iron (Serum) Transferrin Transferrin Saturation Vitamin D (25-OH) Leptin Zinc Selenium Iodine Copper Free T3 (Triiodothyronine) Free T4 (Thyroxine) GGT (Gamma-Glutamyl Transferase)
€799,-
Whoop

Whoop Performance Health

A 50-biomarker performance panel inspired by the WHOOP Performance Health Panel — recovery, blood production, thyroid, hormones, iron and nutrient status for people who train.

Complete Blood Count (CBC) Leukocyte Differential ALP (Alkaline Phosphatase) ALT (Alanine Aminotransferase) AST (Aspartate Aminotransferase) Albumin Total Protein Bilirubin (Total) ApoB (Apolipoprotein B) Total Cholesterol LDL Cholesterol HDL Cholesterol Triglycerides Lipoprotein(a) Urea (BUN) Creatinine eGFR (Estimated Glomerular Filtration Rate) Calcium Bicarbonate Chloride Sodium Potassium Magnesium Cortisol DHEA-S Estradiol (E2) FSH (Follicle Stimulating Hormone) LH (Luteinizing Hormone) SHBG (Sex Hormone Binding Globulin) Total Testosterone Free Testosterone TSH (Thyroid Stimulating Hormone) Glucose (Fasting) HbA1c (Glycated Hemoglobin) Insulin (Fasting) HOMA-IR CRP (C-Reactive Protein) Homocysteine Ferritin Iron (Serum) Transferrin Transferrin Saturation Vitamin D (25-OH) IGF-1 (Insulin-like Growth Factor) Creatine Kinase (CK) Reticulocytes Free T3 (Triiodothyronine) Free T4 (Thyroxine) Vitamin B12 Folate (Folic Acid)
€689,-

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Medical standards

Dr. Naimi oversees the medical standards behind our content and assessments.

Medical policy
CIBG Ministerie van Volksgezondheid,
Welzijn en Sport Official BIG registration BIG 49928676701 Opens in a new tab

TSI (Thyroid Stimulating Immunoglobulin)

€81,-