It is best used in conjunction with other hormone testing such as T4. T-3 uptake is dependent on the number of binding sites of the thyroxine-binding proteins. Any changes in the amount of thyroxine-binding proteins will affect T-3 uptake. T-3 uptake levels can be abnormal with thyroid dysfunction, malnutrition and possibly kidney disease. An abnormal T-3 uptake is associated with oral contraceptives and other endogenous steroid hormones such as testosterone and estrogen.
Test Preparation For Optimal Results:
If possible, have the lab collected early in the morning or shortly after waking. For comparison purposes, have subsequent labs collected close to the same time.
Disclaimer: Your health care provider should evaluate a deviation from normal ranges.