Thyroid-binding globulin (TBG) is produced in the liver and is the primary circulating (transport) protein that binds thyroid hormones 3,5,3’-triiodothyronine (T3) and thyroxine (T4) and carries them in the bloodstream (think of it like a taxi cab that shuttles T3 and T4 around the body).
There are 2 other thyroid hormone transport proteins (Transthyretin & serum Albumin), but TBG has the highest affinity (=the degree to which a substance tends to combine with another) for T4 and T3 but is present in the lowest concentration.
Reference Ranges:
- Adult Male: 12.7-25.1 mcg/mL
- Adult Female 13.5-30.9 mcg/mL
References:
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2417873/
- https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/thyroxine-binding-globulin
Thyroxine-binding globulin, TBG
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