Description
Test Description:
| CODE: | T3 |
| UNITS: | ng/dl |
| TECHNOLOGY: | C.L.I.A |
| FASTING TYPE: | NON FASTING |
| SAMPLE TYPE: | SERUM |
| VOLUME: | 1ml |
| NORMAL RANGE: | 60 – 200 |
Clinical Significance:
Whenever the thyroid function tests i.e. T3, T4, TSH fail to give a diagnostic conclusion, a combination of FT3 and FT4 are requested by the physician.Similar to T4, T3 also circulates in the blood bound to the binding proteins, thyroxine-binding globulin (TBG), thyroxine-binding prealbumin (TBPA) and albumin. The free T3 concentration, which represents about 0.3% of the total circulating hormone concentration, is maintained independently of changes of binding protein levels. The determination of free T3 concentration is a true measure of thyroid status and of cellular metabolism. The free T3 concentration is normal in euthyroid patients with abnormal binding protein levels. The changes in levels of binding proteins are found in certain congenital abnormalities and during pregnancy, use of androgens oral estrogens or contraceptives. Hyperthyroidism is generally associated with an increase of the free T3 concentration. Assessment of this value is of interest in some cases of T3 thyrotoxicosis when free T4 and TSH concentrations in the serum may be within the normal range.A decreased free T3 concentration indicates hypothyroidism. In certain severe non-thyroidal diseases, decreased levels may also be found. Determination of the free T3 concentration allows the follow-up of patients under replacement or suppressive therapy using T3.
