Thyroid-Stimulating Immunoglobulin (TSI)
The antibody that drives Graves' disease and confirms autoimmune hyperthyroidism.
Consider this test if:
- Lab results already show hyperthyroidism (low TSH, high free T4) and you need to confirm Graves' disease
- Symptoms of overactive thyroid: weight loss, palpitations, tremor, heat intolerance, anxiety, or eye changes
- Pregnant or planning pregnancy with a history of Graves' disease, to gauge risk to the baby
- Deciding between antithyroid drugs, radioiodine, or surgery, since high levels predict drug resistance
- Tracking whether antibody levels are falling during treatment or before stopping medication
- HSA/FSA eligible
- Typical results in 2-4 days · Reviewed by a real clinician
- Drawn at a CLIA/CAP-accredited lab near you ·
Pre-test considerations
No fasting required and no specific time of day is needed. A standard blood draw is all that is involved.
Video consult with your Care Team
A 1:1 call to discuss your health.
What members say on Trustpilot
What this test is for
Thyroid-stimulating immunoglobulins are IgG autoantibodies that bind and activate the TSH receptor, pushing the thyroid to overproduce hormone. This test measures those stimulating antibodies and is the most specific way to confirm Graves' disease as the cause of hyperthyroidism, which shows up as weight loss, racing heart, tremor, heat intolerance, anxiety, insomnia, and eye changes. It is most useful once TSH and free T4 already point to an overactive thyroid and you need to know whether autoimmunity is behind it. Markedly elevated TSI also predicts a poorer response to antithyroid drugs and a higher chance of relapse, which informs whether medication, radioiodine, or surgery is the better path. In pregnancy it matters because these antibodies cross the placenta and can cause neonatal hyperthyroidism, so a high maternal level flags the newborn for monitoring.
TSI measures the antibody that actively stimulates the thyroid, which is distinct from TPO antibodies (a marker of autoimmune thyroiditis such as Hashimoto's) and from TSH itself (which measures thyroid function, not its cause).
- Specimen
- Serum
- Measures
- Concentration
What you'll learn
-
Insights that connect the dots. A clinician reads your whole picture, not one result in isolation, connecting family history, past results, and lifestyle into clear next steps.
-
Your personalized action plan. Nutrition, supplements, and training in one clinician-reviewed protocol, updated as your results change.
-
Track your trends. Upload results from any lab and see each biomarker trend over time, so you know what is working.
-
Never miss a recheck. Mito tells you what is worth retesting and when, then reminds you so nothing slips.
What to expect
- 1 Book instantly
Click, book, done. Choose a convenient lab location near you. Transparent, up-front pricing.
- 2 Quick lab visit
Testing to fit your busy schedule, usually 15 minutes or less. Walk-in and appointments available.
- 3 Typical results in 2-4 days
Your results post straight to your dashboard as soon as the lab completes them.
- 4 Expert guidance
Included with Mito membership. A clinician reviews your results and your personalized action plan follows, with clear next steps.
Everything your health needs,
in one membership
-
Every test at our cost
Members pay our cost on every test, with lab fees passed straight through. The full receipt is itemized, never padded.
-
Continuous tracking, all in one place
Upload past labs and watch your trends over time. Every marker and visit lives in one longitudinal record, so all your care stays together.
-
Year-round clinician support
Text anytime and get clinician-reviewed answers. When you want to go deeper, 1:1 consultations are available at affordable rates.
All for $9/month
Order any test or consult without joining. For $9/month, members unlock member prices, trend tracking, and year-round clinician guidance.
Mito Membership
$9 /mo
cancel anytime
Without membership
$0
pay as you go
At-cost pricing on labs, scans, and more
Supplements at 30% off retail prices Coming soon
On-demand clinician consults when you need guidance
Personalized action plans across supplements, exercise, nutrition, and sleep
AI health coaching to help you act on your results
Year-round medical support, with in-chat clinician escalation
All your health records in one personal vault, with trends and biological age tracking
Early access to new diagnostics and product releases
More tests to consider
Loading essentials…
Frequently asked questions
View all FAQsHow does pricing work?
Every test shows the member price next to the standard non-member price, so you can see what membership saves you. The member price is our cost, covering the lab and what it takes to run the service. It is never a profit on the test itself. Mito makes its money on the $9 membership, not on marking up your tests. Membership is $9 per month, and any applicable lab order or draw fee is itemized before you pay.
Where do I get tested?
Choose an available partner lab at checkout. If your cart contains multiple blood tests, Mito helps consolidate the eligible tests at one lab when possible. At-home kits and scans follow the collection or appointment process shown on their product page.
Is this eligible for HSA/FSA?
Yes. Eligible tests can be paid for with an HSA or FSA card at checkout.
When will I get my results?
Your results appear in your Mito dashboard after the laboratory completes processing. A clinician then reviews them before your analysis and personalized action plan are finalized. Timing varies by test, and specialty assays and at-home kits may take longer.
Do I need a physician's order?
No. Mito provides the laboratory order when one is required, so you do not need to arrange a separate physician visit before purchasing.
Recently viewed
Loading essentials…