Thyroid-Stimulating Immunoglobulin (TSI)
An autoantibody that mimics TSH and switches the thyroid on continuously — the direct cause of Graves' disease.
The confirmatory test for Graves' disease, the most common cause of hyperthyroidism. Distinguishes it from thyroiditis and other causes, which are managed completely differently.
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🩸 Test your Thyroid-Stimulating Immunoglobulin (TSI)
Order directly through Marek Diagnostics — no doctor's visit needed, drawn at any Quest location in the US. Code CAMERON applies 10% off automatically.
Order this test — 10% off → Browse all 102 markers →What Thyroid-Stimulating Immunoglobulin (TSI) is usually tested alongside
On its own, one marker is a data point. These panels include Thyroid-Stimulating Immunoglobulin (TSI) plus the markers that make it interpretable — each names every test, why it is on the list, and loads the whole set into your cart in one click at 10% off.
includes this + 8 more markers — Abnormal TSH, a goitre, a family history of thyroid disease, postpartum thyroid changes, or thyroid symptoms with 'normal' basic labs.
Would you feel it? Symptoms Thyroid-Stimulating Immunoglobulin (TSI) helps explain
People rarely search for a marker — they search for how they feel. These are the complaints where this marker is worth checking, and whether it is a first-line test or a follow-up once the obvious causes are ruled out.
Why your Thyroid-Stimulating Immunoglobulin (TSI) might be wrong
Most abnormal results are interference, not disease. These are the things that measurably move this specific marker — check them before you change anything. Each one says whether the number is wrong and should be repeated, badly timed and should be redrawn, or real with a cause worth explaining.
Biotin interferes with the streptavidin-biotin immunoassays most hormone tests run on. Depending on the assay design it pushes the result falsely HIGH or falsely LOW — there is no single direction to correct for. Hair, skin and nail products are the usual source, and doses in those are far above the RDA.
Stop biotin 48–72 hours before the draw, and check every supplement label rather than just the one labelled biotin.
Treatment changes titres over months, so a value only means something alongside where you are in treatment.
Note treatment status and dates on the result.
What Thyroid-Stimulating Immunoglobulin (TSI) means in combination
A single marker tells you a little. Combinations tell you the story — these are the named patterns this marker takes part in, and what each one points at.
Thyroid stimulating immunoglobulin is what distinguishes Graves' disease from the destructive thyroiditis that produces an identical early picture. The distinction decides the treatment: Graves' is overproduction and responds to antithyroid drugs, thyroiditis is leakage and does not.
A doctor's call. Postpartum, the timing also matters — the hyperthyroid phase of postpartum thyroiditis is TSI-negative and resolves on its own.
What to test next
Markers rarely answer alone. These are the ones that put Thyroid-Stimulating Immunoglobulin (TSI) in context — each with its own full breakdown.
Frequently asked questions
<140% baseline activity (assay dependent) Ranges vary by laboratory and assay — always compare to the range printed on your own report.
Optimal ranges, root causes and the full correction protocol are available inside Coach Cam's Peptide Academy.
See the full breakdown inside the Academy.
See the full breakdown inside the Academy.
You can order Thyroid-Stimulating Immunoglobulin (TSI) directly through Marek Diagnostics without a doctor's visit — drawn at any Quest Diagnostics location in the US. Code CAMERON applies 10% off automatically.