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  • Test Details
  • Lab Values
  • Clinical Significance
  • Treatment Options
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Test Code 1014

Test Details

Total T3 (Triiodothyronine or T3)

Total T3 (triiodothyronine) is a hormone generated by converting T4 to T3 in the body’s tissue. T3 is the active thyroid hormone and is necessary for normal body metabolism.

Methodology

Chemiluminescence immunoassay

Patient Preparation

None

Preferred Specimen

1.0 mL serum collected in a serum separator tube (SST / Tiger Top)

Alternate Specimen

None

Transport Temperature

Refrigerated (ship on frozen cold packs)

Stability

Refrigerated: 14 days

Lab Values

Lab Values

Total T3 (Triiodothyronine or T3)

  • Low: <0.8 ng/mL
  • Optimal: 0.8-2.0 ng/mL
  • High: >2.0 ng/mL
Test Details
Clinical Significance

Clinical Significance

Total T3 (Triiodothyronine or T3)

  • Low Total T3 levels are consistent with hypothyroidism or inadequate thyroid hormone replacement.1-3
  • High Total T3 levels are consistent with either hyperthyroidism or excess thyroid hormone replacement.1-3
  • High doses of biotin (> 5 mg/day) may interfere with assay results. Patient assumed to be refraining from biotin supplementation for at least 3 days prior to blood draw.

References:

  1. 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.
  2. 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.
  3. 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.
Lab Values
Treatment Options

Treatment Options

Total T3 (Triiodothyronine or T3)

Treatment is based on cause of Total T3 elevation/reduction.

Clinical Significance