Lab test
TSI Test - Thyroid Stimulating Blood Test
TSI Test - Thyroid Stimulating Blood Test can be ordered without a referral, and this guide covers what to expect. This blood test measures thyroid-stimulating immunoglobulin (TSI) levels to help assess thyroid function.
What this test is
Thyroid-stimulating immunoglobulin (TSI) is an antibody that can mimic the action of thyroid-stimulating hormone (TSH). High levels of TSI can indicate an overactive thyroid.
What it measures
- Thyroid Stimulating Immunoglobulin (TSI) — measures antibodies that stimulate the thyroid gland
What the test involves
This test requires a standard blood draw from a vein in your arm.
Why it is often ordered
Clinicians often order this test to help diagnose or monitor Graves' disease, an autoimmune condition affecting the thyroid. It can also be used to evaluate the cause of hyperthyroidism.
Preparation
No specific preparation is usually required for this test. Please follow any instructions provided by the laboratory where you will have your blood drawn.
How results are reported
Results are typically reported within a few business days. Reference ranges, which indicate the expected values for healthy individuals, vary between laboratories.
Before you go
- Turnaround time
- Specific preparation instructions
- How to access your results
FAQ
Frequently asked questions
What is Graves' disease?
Graves' disease is an autoimmune disorder where the body's immune system mistakenly attacks the thyroid gland. This attack can lead to an overproduction of thyroid hormones, a condition known as hyperthyroidism.
Can TSI levels affect pregnancy?
Yes, high TSI levels in pregnant individuals can potentially cross the placenta and affect the baby's thyroid function. Monitoring is important during pregnancy.
How is TSI different from TSH?
TSH (Thyroid-Stimulating Hormone) is a hormone produced by the pituitary gland that tells the thyroid to make thyroid hormones. TSI is an antibody that can act like TSH, but it is produced by the immune system and can cause overactivity.
What does it mean if my TSI levels are high?
High TSI levels generally suggest that your immune system is stimulating your thyroid gland, potentially leading to hyperthyroidism or Graves' disease. Your clinician will interpret these results in the context of your overall health.
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