Thyroxine Binding Globulin (TBG)
The main carrier protein for thyroid hormone — the thyroid equivalent of SHBG.
Explains confusing thyroid panels where total T4/T3 look abnormal but free levels are fine. Changes in TBG shift total hormone without affecting the active free fraction.
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🩸 Test your Thyroxine Binding Globulin (TBG)
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 Thyroxine Binding Globulin (TBG) is usually tested alongside
On its own, one marker is a data point. These panels include Thyroxine Binding Globulin (TBG) 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 Thyroxine Binding Globulin (TBG) 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 Thyroxine Binding Globulin (TBG) 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.
Oestrogen substantially raises thyroid-binding globulin. That raises TOTAL T4 and T3 while free hormone stays normal, which is why total thyroid hormones mislead in anyone on oestrogen.
Use free T4 and free T3, not totals, if you are on oestrogen or pregnant.
Lower TBG, producing the mirror-image error in the other direction.
Same answer: read the free hormones.
What Thyroxine Binding Globulin (TBG) 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.
Oestrogen — the pill, HRT or pregnancy — raises thyroid-binding globulin substantially. That lifts TOTAL thyroid hormones while the free, biologically active fraction stays completely normal. It is the classic reason totals mislead in anyone on oestrogen.
Use free T4 and free T3, never totals, if you are on oestrogen or pregnant. Androgens and steroids produce the mirror-image error downward.
What to test next
Markers rarely answer alone. These are the ones that put Thyroxine Binding Globulin (TBG) in context — each with its own full breakdown.
Frequently asked questions
13–39 µg/mL 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 Thyroxine Binding Globulin (TBG) directly through Marek Diagnostics without a doctor's visit — drawn at any Quest Diagnostics location in the US. Code CAMERON applies 10% off automatically.