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Test Code THSCM Thyroid Function Cascade, Serum

Reporting Name

Thyroid Function Cascade, S

Useful For

Screening for a diagnosis of thyroid disease

Profile Information

Test ID Reporting Name Available Separately Always Performed
STSHC TSH, Sensitive, S Yes, (order STSH) Yes

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
FRT4C T4 (Thyroxine), Free, S Yes, (order FRT4) No
TPOC Thyroperoxidase Ab, S Yes, (order TPO) No
T3C T3 (Triiodothyronine), Total, S Yes, (order T3) No

Testing Algorithm

If thyroid-stimulating hormone (TSH) is <0.3 mIU/L, then free T4 (FT4) is performed at an additional charge.


If FT4 is normal and the TSH is <0.1 mIU/L, then triiodothyronine (T3) is performed at an additional charge.


If TSH is >4.2 mIU/L, then FT4 and thyroperoxidase antibodies are performed at an additional charge.


See Thyroid Function Ordering Algorithm in Special Instructions.

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type


Specimen Required

Patient Preparation:

1. For 12 hours before specimen collection do not take multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins.

2. In patients receiving therapy with high biotin doses (ie, >5 mg/day), no specimen should be taken until at least 8 hours after the last biotin administration.


Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 1.5 mL

Collection Instructions:

1. Serum gel tubes should be centrifuged within 2 hours of collection.

2. Red-top tubes should be centrifuged and aliquoted within 2 hours of collection.

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 7 days
  Frozen  30 days
  Ambient  72 hours

Reference Values

0-5 days: 0.7-15.2 mIU/L

6 days-2 months: 0.7-11.0 mIU/L

3-11 months: 0.7-8.4 mIU/L

1-5 years: 0.7-6.0 mIU/L

6-10 years: 0.6-4.8 mIU/L

11-19 years: 0.5-4.3 mIU/L

≥20 years: 0.3-4.2 mIU/L

Day(s) and Time(s) Performed

Monday through Sunday; Continuously

Test Classification

This test has been cleared, approved or is exempt by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

84443-Thyroid-stimulating hormone-sensitive (s-TSH)

84439-T4 (thyroxine), free (if appropriate)

84480-T3 (triiodothyronine), total (if appropriate)

86376-Thyroperoxidase (TPO) antibodies (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
THSCM Thyroid Function Cascade, S 11579-0


Result ID Test Result Name Result LOINC Value
STSHC TSH, Sensitive, S 11579-0

Reject Due To

Gross hemolysis Reject
Gross lipemia OK
Gross icterus OK

Method Name

Electrochemiluminescent Immunoassay