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General
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Clinical Use:
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Thyroid hormone is secreted from the thyroid into the circulation as thyroxine and tri-iodothyronine (T3). A substantial part of the circulating T3 is derived from extra-thyroidal deiodination of T4. Like T4 it is transported in the serum bound to serum protein. Thyroxine Binding Globulin binds approximately 80% of T3 (although its affinity for TBG is considerably less than that of T4), Thyroxine Binding Pre Albumin approximately 10% and Albumin approximately 10%. It is thought that normal levels of free T3 (the biologically active part) contribute significantly to the euthyroid state.
Usually there is a good correlation between T3 and T4 levels over a wide range of concentrations. However, sometimes the changes are independent of one another. Abnormal T3 levels are an indication of malfunction of the thyroid gland and are an important part of the investigation of the dysfunction of the hypothalamic/pituitary/thyroid axis. T3 levels are useful in the confirmation of thyrotoxicosis.
The direct measurement of free T3 enables thyroid function measurement even with abnormal liver function tests, TBG fluctuations during pregnancy as well as TBG defects and abnormally high TBG levels. |
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Availability:
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Samples are tested routinely during the testing laboratory's hours of operation. |
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Aliases/Synonyms:
| FT3, T3, Triiodothyronine, |
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Code:
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FT3 |
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Handling Instructions (to laboratory):
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Send sample chilled. |
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Hyperlink:
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Reference Interval:
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0 days to <31 days: 3.0 - 8.0 pmol/L
31 days to <1 year: 3.5 - 7.5 pmol/L
1 year to <6 years: 4.0 - 7.0 pmol/L
6 years to <11 years: 4.0 - 6.5 pmol/L
11 years to <15 years: 3.0 - 6.5 pmol/L
15 years to <19 years: 3.0 - 6.0 pmol/L
19 years to <120 years: 3.0 - 5.5 pmol/L
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Collection Requirements
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Container:
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Serum Sep. Tube-SST (GOLD), |
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Sample Type:
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See container |
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Minimum Collection Volume:
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1mL |
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Collection Instructions:
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Processing Requirements
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Alternate Containers:
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Lithium Heparin-PST (GREEN) |
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Processing Instructions:
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Minimum Assay Volume:
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75uL |
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Stability:
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14 days chilled |
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Transport Instructions (to testing laboratory):
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Send sample chilled. |
Testing Locations
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Performed at:
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Section
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Department
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Site
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Contact Phone
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| Core |
Biochemistry |
Fiona Stanley Hospital |
6152 8140 |
| Core |
Biochemistry |
QEII Medical Centre |
6383 4093 |
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Last Updated : 07-10-2020 13:42 |