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TBG Unit Converter
Thyroxine-Binding Globulin (TBG) is the major transport protein for thyroid hormones (T4 and T3) in the blood. It binds approximately 75% of circulating thyroxine.
Measuring TBG is useful for distinguishing between total T4 abnormalities caused by binding protein changes (e.g., pregnancy, oral contraceptives) versus true thyroid dysfunction. This converter facilitates switching between standard mass units (μg/mL) and SI molar units (nmol/L).
Mass Units
StandardMicrograms per milliliter (Numerically equivalent to mg/L).
SI Units / Molar
Nanomoles per liter (International Standard).
Clinical Context
Reference Ranges (Adults): Typically 13 – 39 μg/mL (240 – 720 nmol/L).
Interpretation:
• High TBG: Pregnancy, Estrogen therapy, Hepatitis, Acute Intermittent Porphyria.
• Low TBG: Androgens/Steroids, Nephrotic Syndrome, Major Illness/Stress, Acromegaly.
Conversion Logic:
Molecular Weight of TBG: ~54,000 Da (54 kDa).
1 μg/mL ≈ 18.5 nmol/L.
1 nmol/L ≈ 0.054 μg/mL.
Clinical References
How to Use This Converter
Follow these steps to normalize TBG values.
Enter Values
Input your laboratory result into the corresponding unit field (e.g., μg/mL).
Automatic Conversion
The calculator converts between mass units and the SI molar unit using the molecular weight of 54 kDa.
Reset
Use the Clear button to reset all fields.
Frequently Asked Questions
Yes. 1 microgram per milliliter is numerically identical to 1 milligram per liter.
If Total T4 is high but Free T4 is normal, measuring TBG can confirm that the elevation is due to increased binding proteins (like in pregnancy) rather than hyperthyroidism.