Test Code 1005R
Test Details
Thyroid Stimulating Hormone (TSH) w/Reflex to TT3 & FT4
TSH is a peptide hormone synthesized and secreted by the anterior pituitary gland. TSH regulates thyroid gland function.
When TSH is not in the optimal range (0.27-4.20 µlU/mL), Free T4 and Total T3 are also tested to aid in the determination of hyperthyroidism and hypothyroidism.
Methodology
Immunoassay
Patient Preparation
None
Preferred Specimen
1.0 mL serum (0.5 mL minimum) collected in serum separator tube (SST/Tiger Top)
Alternate Specimen
None
Transport Temperature
Refrigerated (ship on frozen cold packs)
Stability
Refrigerated: 14 days
Lab Values
Thyroid Stimulating Hormone (TSH) w/Reflex to TT3 & FT4
TSH
| Age | Low | Optimal | High |
| <5 yrs | Not Established | ||
| 5 – 10 yrs | <0.60 µlU/mL | 0.60 – 4.84 µlU/mL | >4.84 µlU/mL |
| 11 – 18 yrs | <0.45 µlU/mL | 0.45 – 4.50 µlU/mL | >4.50 µlU/mL |
| >18 | <0.27 µlU/mL | 0.27 – 4.20 µlU/mL | >4.20 µlU/mL |
Free T4
- Low: <0.93 ng/dL
- Optimal: 0.93-1.70 ng/dL
- High: >1.70 ng/dL
Total T3
- Low: <0.8 ng/mL
- Optimal: 0.8-2.0 ng/mL
- High: >2.0 ng/mL
Clinical Significance
Thyroid Stimulating Hormone (TSH) w/Reflex to TT3 & FT4
- TSH is used in the differential diagnosis of primary, secondary, & tertiary hypothyroidism.1-3
- Is also useful in screening for hyperthyroidism.1-3
- Allows adjustment of thyroid replacement in hypothyroid patients.1-3
- These assays no longer show biotin interference in serum concentrations up to 1200 ng/mL.
References:
References:
- Goodman N, Cobin RH. Reproductive disorders. In: Camacho PM, Gharib H, Sizemore GW, eds. Evidence-Based Endocrinology. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins. 2012:190-228.
- Castro MR, Gharib H. Thyroid disorders. In: Camacho PM, Gharib H, Sizemore GW, eds. Evidence-Based Endocrinology. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins. 2012:43-80.
- Garber JR, Cobin RH, Gharib H, et al. Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Endocr Pract. 2012;18(6):988-1028.
Treatment Options
Thyroid Stimulating Hormone (TSH) w/Reflex to TT3 & FT4
- Low value is consistent with either an overactive thyroid gland or excess thyroid hormone replacement.
- High value is consistent with an underactive thyroid gland or inadequate thyroid hormone replacement.
