TSH w/Reflex
Test Mnemonic
TSHRF
CPT Codes
- 84443 - QTY (1)
Aliases
- Thyroid Stimulating Hormone with reflex Thyroxine Free
Performing Laboratory
Cleveland Clinic Laboratories
Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 1 mL | Plasma | Lithium heparin PST (Lt. Green) | Ambient | Centrifuge and refrigerate. |
Alternate Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 1 mL | Serum | SST (Gold) | Ambient |
Stability
| Environmental Condition | Description |
|---|---|
| Ambient | 5 days |
| Refrigerated | 7 days |
| Frozen | 30 days |
Days Performed
7 days a week
Turnaround Time
8 hours
Methodology
| Name | Description |
|---|---|
| Electro Chemiluminescence Immunoassay (ECLIA) |
Clinical Info
Produced by the anterior pituitary gland, thyroid-stimulating hormone (TSH) stimulates the thyroid gland to convert iodine and the amino acid tyrosine into the thyroid hormones thyroxine (T4) and triiodothyronine (T3), which in turn regulate metabolism, growth, and development. These free thyroid hormones also work in a negative feedback loop to regulate the amount of TSH that is released from the pituitary gland. Testing for TSH is a highly sensitive indicator for hypothyroidism and an important tool in diagnosing thyroid dysfunction. An elevated TSH result usually indicates an underactive thyroid (hypothyroidism), and a decreased TSH result indicates an overactive thyroid (hyperthyroidism) or excessive amounts of thyroid medication in an individual being treated for hypothyroidism. The latest “third-generation†assays for TSH are sensitive enough to distinguish moderately low but still clinically normal levels of TSH from lower levels indicative of hyperthyroidism. If TSH is abnormal, Free T4 will be performed and billed.