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Free Thyroxine
MessageAlong with Free T3, Free T4 regulates normal growth and development by maintaining body temperature and stimulating calorigenesis. They also affect all aspects of carbohydrate metabolism as well as certain areas of lipid and vitamin metabolism.
Test Code
FT4
Alias/See Also
LAB3060006
FT4
FT4
CPT Codes
84439
Preferred Specimen
2.0 mL serum collected in a gold serum separator tube (SST)
Minimum Volume
0.5 mL serum
Other Acceptable Specimens
2.0 mL serum collected in an orange rapid clot serum separator tube (RCT)
Specimen Stability
Store centrifuged samples tightly stoppered at room temperature 15 - 30oC for no longer than eight hours. If the assay will not be completed within eight hours, refrigerate the samples at 2 - 8oC. If the assay will not be completed within 48 hours, or for shipment of samples, freeze serum at -20oC or colder.
Methodology
Immunoassay
Limitations
High dose Biotin Supplementation can cause falsely increased or decreased results.
Reference Range
| Sex | Age | Reference Range |
|---|---|---|
| M | 0 - 3 days | 0.80 - 2.78 ng/dL |
| F | 0 - 3 days | 0.88 - 1.93 ng/dL |
| M | 3 days - 1 month | 0.48 - 2.32 ng/dL |
| F | 3 days - 1 month | 0.61 - 1.93 ng/dL |
| M | 1 -12 months | 0.76 - 2.00 ng/dL |
| F | 1 - 12 months | 0.88 - 1.84 ng/dL |
| M | 1 - 5 years | 0.90 - 1.59 ng/dL |
| F | 1 - 5 years | 1.02 - 1.72 ng/dL |
| M | 5 - 10 years | 0.81 - 1.68 ng/dL |
| F | 5 - 10 years | 0.82 - 1.58 ng/dL |
| M | 10 - 15 years | 0.92 - 1.57 ng/dL |
| F | 10 - 15 years | 0.79 - 1.49 ng/dL |
| M | 15 - 18 years | 0.92 - 1.53 ng/dL |
| F | 15 - 18 years | 0.83 - 1.44 ng/dL |
| M/F | 18 - 150 years | 0.40 - 1.64 ng/dL |
Performing Laboratory
Penn Medicine Lancaster General Health
