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Triiodothyronine, Total, serum and plasma

Alternate test name

T3, Total

Lab area
Clinical Biochemistry - General
Method and equipment
Abbott Ci-4100
Expected turn-around time
STAT: 24 Hours Urgent: 24 Hours Routine: 24 Hours
Specimen type

Serum, Sodium/Lithium Heparin / Potassium EDTA

Specimen requirements

150 uL

Storage and transportation


Shipping information
The Hospital for Sick Children
Rapid Response Laboratory
555 University Avenue, Room 3642
Toronto, ON
M5G 1X8
Phone: 416-813-7200
Toll Free: 1-855-381-3212
Hours: 7 days/week, 24 hours/day
Background and clinical significance

3,5,3’ Triiodothyronine (T3) is a thyroid hormone with a molecular weight of 651 daltons and a half-life in serum of 1.5 days. T3 circulates in the blood as an equilibrium mixture of free and protein bound hormone. T3 is bound to thyroxine binding globulin (TBG), prealbumin, and albumin It has become apparent in recent years that T3 plays an important role in the maintenance of the euthyroid state. Serum T3 measurements can be a valuable component of a thyroid screening panel in diagnosing certain disorders of thyroid function as well as conditions caused by iodine deficiency. Clinically, measurements of serum T3 concentration are especially valuable in diagnosing hyperthyroidism and in following the course of therapy for this disorder.

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