Lab Test

Thyroid Stimulating Hormone (TSH), 3rd Generation

Thyrotropin

Test Codes

Antrim #16970: EPIC: LAB7030, TSHG, Cord Blood: EPIC: LAB6598, TSHCB

Department

Chemistry

Specimen Collection Criteria

Collect: One Gold-top SST tube (adults) or one full Gold-top Microtainer® (pediatric). (Minimum Whole Blood: 4.0 mL)

Contact the Laboratory for the acceptability of other tube types.
See Minimum Pediatric Specimen Requirements for Microtainer® collection.

Physician Office/Draw Specimen Preparation

Let SST specimens clot for 30-60 minutes then immediately centrifuge to separate serum from cells. Refrigerate (2-8°C or 36-46°F) the centrifuged SST tube within two hours of collection. (Minimum: 1.0 mL)

Preparation for Courier Transport

Transport: Centrifuged SST tube, refrigerated (2-8°C or 36-46°F). (Minimum: 1.0 mL)

Rejection Criteria

Grossly hemolyzed specimens.

Red-top tubes with serum not separated from cells within two hours of collection.

In-Lab Processing

Let SST specimens clot 30-60 minutes. Centrifuge SST tubes or Microtainers® to separate serum from cells. Deliver immediately to the appropriate testing station.

Storage

Specimen Stability for Testing:

Centrifuged SST Tubes and Microtainers® with Separator Gel
Room Temperature (20-26°C or 68-78.8°F): 2-4 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Red-top Tubes and Microtainers® without Separator Gel
Room Temperature (20-26°C or 68-78.8°F): 2-4 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Serum Specimens (Pour-Overs)
Room Temperature (20-26°C or 68-78.8°F): 2-4 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 7 days

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days

Laboratory

Dearborn Chemistry Laboratory
Farmington Hills Chemistry Laboratory
Grosse Pointe Chemistry Laboratory
Royal Oak Automated Chemistry Laboratory
Taylor Chemistry Laboratory
Trenton Chemistry Laboratory
Troy Chemistry Laboratory
Wayne Chemistry Laboratory 

Performed

Sunday – Saturday, 24 hours a day. 
Results available within 24 hours of receipt in the Chemistry Laboratory.

Reference Range

TSH (3rd Generation)

Cord Blood: 1.00 – 39.00 mcIU/mL.
1 Year – Adult 0.40 – 4.50 mcIU/mL. 
Pediatric Ranges: 
0 - 2 Days:  3.20 – 34.60 mcIU/mL. 
3 - 4 Days 0.70 – 15.40 mcIU.mL.
5 Days – < 1 Months 1.70 – 9.10 mcIU/mL.
1 Month – < 1 Year 0.80 – 8.20 mcIU/mL. 


TSH (3rd Generation) Pregnancy

1st Trimester: 0.26 - 2.66 mcIU/mL
2nd Trimester: 0.55 - 2.73 mcIU/mL.
3rd Trimester: 0.43 - 2.91 mcIU/mL.

 

Test Methodology

Chemiluminescent Immunoassay.

Interpretation

Hypothyroidism: Elevated TSH substantiated by clinical correlation
Hyperthyroidism: Depressed TSH substantiated by clinical correlation


Heterophilic antibodies in human serum can react with reagent immunoglobulins, interfering with in vitro immunoassays. Patients routinely exposed to animals or animal serum products can be prone to this interference and anomalous high values can be observed. Additional information may be required for diagnosis.

TSH levels during the first trimester of pregnancy, or whenever very high levels of hCG are present, should be interpreted with caution.

Clinical Utility

TSH levels aid in evaluating thyroid function and replacement therapy. They are especially useful in the differential diagnosis of primary (thyroid) from secondary (pituitary) and tertiary (hypothalamus) hypothyroidism. In primary hypothyroidism, TSH levels are significantly elevated, while in secondary and tertiary hypothyroidism, TSH levels are low or normal.

When testing patients on thyroid hormone replacement, blood should be obtained shortly before the patients next dose. Testing shortly after thyroid hormone intake should not affect TSH results, however it may result in an apparently elevated free T4. If a patient's dose of thyroid hormone is changed, it is recommended that 6-8 weeks be allowed to elapse before retesting.

CPT Codes

84443
LOINC:  11579-0, Cord Blood 69561-9

Contacts

Last Updated

8/2/2021

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