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Test Code LAB1402 Thyroid Function Cascade, Serum

Additional Codes

Mayo Test ID
THSCM

 

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 thyrotropin (TSH, formerly thyroid-stimulating hormone) is less than 0.3 mIU/L, then free T4 (thyroxine) is performed at an additional charge.

 

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

 

If TSH is greater than 4.2 mIU/L, then free T4 and thyroperoxidase antibodies are performed at an additional charge.

 

For more information see Thyroid Function Ordering Algorithm.

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Serum


Specimen Required


Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

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 the serum aliquoted into a plastic vial 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) Performed

Monday through Sunday

Test Classification

This test has been cleared, approved, or is exempt by the US 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

84439 (if appropriate)

84480 (if appropriate)

86376 (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

Interpretation

In primary hypothyroidism, thyrotropin (TSH, formerly thyroid-stimulating hormone) levels will be elevated. In primary hyperthyroidism, TSH levels will be low.

 

The ability to quantitate circulating levels of TSH is important in evaluating thyroid function. It is 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.

 

Elevated or low TSH in the context of normal free thyroxine is often referred to as subclinical hypo- or hyperthyroidism, respectively.

 

Thyrotropin-releasing hormone (TRH) stimulation differentiates all types of hypothyroidism by observing the change in patient TSH levels in response to TRH. Typically, the TSH response to TRH stimulation is exaggerated in cases of primary hypothyroidism, absent in secondary hypothyroidism, and delayed in tertiary hypothyroidism. Most individuals with primary hyperthyroidism have TSH suppression and do not respond to TRH stimulation test with an increase in TSH over their basal value.

 

Sick, hospitalized patients may have falsely low or transiently elevated TSH.

Report Available

1 to 2 days

Specimen Retention Time

7 days

Reject Due To

Gross hemolysis Reject
Gross lipemia OK
Gross icterus OK

Method Name

Electrochemiluminescent Immunoassay