T4, Total Unit Converter
Convert between nmol/L, µg/dL, µg/L, ng/mL
Also known as: T4, TT4, Total Thyroxine, Thyroxine Total, Serum Thyroxine
Convert T4, Total
What is T4, Total?
Total T4 (thyroxine) measures the combined amount of bound and unbound thyroxine in your blood. Thyroxine is the primary hormone produced by your thyroid gland.
Most T4 in your blood (about 99%) is bound to carrier proteins, primarily thyroxine-binding globulin (TBG). Only a small fraction circulates as free T4, which is the biologically active form that enters cells.
T4 itself is relatively inactive. It serves as a prohormone that gets converted to the more potent triiodothyronine (T3) in tissues like the liver and kidneys.
Where Does T4, Total Come From?
T4 is produced exclusively by the thyroid gland, a butterfly-shaped gland in the front of your neck. The thyroid releases T4 in response to thyroid-stimulating hormone (TSH) from the pituitary gland.
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