Thyroid Stimulating Hormone (TSH)

Cleveland Heartlab T, Test, Thyroid Function

CPT Code: 84443

Order Code:
Thyroid Stimulating Hormone (TSH): C157

Reflex Order Codes:
TSH with Reflex to Free T4: C513
If TSH is <0.500 uIU/mL or >4.500 uIU/mL then Free T4 (FT4) will be performed at an additional charge (CPT 84439).

ABN Requirement:  
Synonyms: TSH
Specimen: Serum
Volume: 0.5 mL
Minimum Volume: 0.2 mL
Container: Gel-barrier tube (SST, Tiger Top)


  1. Collect and label sample according to standard protocols.
  2. Gently invert tube 5 times immediately after draw. DO NOT SHAKE.
  3. Allow blood to clot 30 minutes.
  4. Centrifuge for 10 minutes.

Special Instructions: Samples should not be taken from patients receiving therapy with high biotin doses (>5 mg/day) until at least 8 hours following the last dose.

Transport: Store serum at 2°C to 8°C after collection and ship the same day per packaging instructions included with the provided shipping box.


Ambient (15-25°C): not acceptable
Refrigerated (2-8°C): 14 days
Frozen (-20°C): 24 months

Causes of Rejection: Specimens other than serum; improper labeling; samples not stored properly; samples older than stability limits

Methodology: Electrochemiluminescence Immunoassay (ECLIA)

Turn Around Time: 1 to 3 days

Reference Range:

Age uIU/mL
0-2 days 3.200-34.600
3-4 days 0.700-15.400
5-13 days 0.700-11.900
14-30 days 1.700-9.100
31 days-5 months 1.700-9.100
6-24 months 0.800-8.200
25 months-3 years 0.400-5.500
≥4 years 0.400-4.500
Priority 2 Value (uIU/mL)

≤1 year≥40.000

Clinical Significance: For differential diagnosis of primary, secondary, and tertiary hypothyroidism. Also useful in screening for hyperthyroidism. This assay allows adjustment of exogenous thyroxine dosage in hypothyroid patients and in patients on suppressive thyroxine therapy for thyroid neoplasia.

Limitations: The presence of autoantibodies may induce high molecular weight complexes (macro-TSH) which may cause unexpected high values of TSH. In rare cases, interference due to extremely high titers of antibodies to analyte-specific antibodies, streptavidin or ruthenium can occur.

Additional Information: Serum TSH levels exhibit a diurnal variation with the peak occurring during the night. The lowest levels occur between 10 am and 4 pm, and reach 50% of the peak.

The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.