Thyroid-stimulating Hormone (TSH) and Free T4
Also known as: TSH and Free T4
Use
The Thyroid-stimulating Hormone (TSH) and Free T4 test is used to evaluate thyroid function and to monitor treatment for thyroid conditions. TSH is produced by the pituitary gland and regulates thyroid hormone release. Free T4 is a direct measure of thyroxine level in the blood, which is crucial for diagnosing hyperthyroidism or hypothyroidism. Monitoring these hormones is essential for patients under thyroid hormone therapy or those with conditions affecting the pituitary or thyroid glands.
Special Instructions
This test may exhibit interference when the sample is collected from a patient who is consuming a supplement with a high dose of biotin. Patients should be asked about biotin supplementation and instructed to cease biotin intake at least 72 hours before sample collection to avoid interference with test results.
Limitations
The test has limitations including interference from biotin supplementation, which can affect the assay performance and lead to inaccurate results. The minimum volume required does not allow for repeat testing. Other factors such as improper labeling, incorrect specimen type, or delayed processing can cause sample rejection or affect results. Citrate plasma specimens are specifically noted as unsuitable for this test.
Methodology
Immunoassay (ECLIA)
Biomarkers
LOINC Codes
- 11580-8
- 3024-7
- 11580-8
- 3024-7
Result Turnaround Time
1 day
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
1 mL
Minimum Volume
0.7 mL
Container
Red-top tube, gel-barrier tube
Collection Instructions
If a red-top tube is used, transfer separated serum to a plastic transport tube.
Patient Preparation
Patients should cease biotin intake at least 72 hours before sample collection.
Storage Instructions
Store at room temperature.
Causes for Rejection
Citrate plasma specimen; improper labeling
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 7 days |
| Refrigerated | 14 days |
| Frozen | 14 days |