Test Catalog

Test Id : T3

T3 (Triiodothyronine), Total, Serum

Useful For
Suggests clinical disorders or settings where the test may be helpful

Second-order testing for hyperthyroidism in patients with low thyroid-stimulating hormone values and normal thyroxine levels

 

Diagnosis of triiodothyronine toxicosis

 

This test is not useful for general screening of the population without a clinical suspicion of hyperthyroidism.

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

See Thyroid Function Ordering Algorithm in Special Instructions.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Name
A short description of the method used to perform the test

Electrochemiluminescence Immunoassay

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.

Yes

Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

T3 (Triiodothyronine), Total, S

Aliases
Lists additional common names for a test, as an aid in searching

T3 Suppression

T3 Total, Serum

Total T3, Serum

Triiodothyronine (T3)

Triiodothyronine, Total T3

Thyroid Function Cascade

T3 (Triiodothyronine), Total Only, Serum

Triiodothyronine

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

See Thyroid Function Ordering Algorithm in Special Instructions.

Specimen Type
Describes the specimen type validated for testing

Serum

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Patient Preparation: 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.

Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.75 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis Reject
Gross lipemia OK
Gross icterus OK

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

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

Useful For
Suggests clinical disorders or settings where the test may be helpful

Second-order testing for hyperthyroidism in patients with low thyroid-stimulating hormone values and normal thyroxine levels

 

Diagnosis of triiodothyronine toxicosis

 

This test is not useful for general screening of the population without a clinical suspicion of hyperthyroidism.

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

See Thyroid Function Ordering Algorithm in Special Instructions.

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Thyroid hormones regulate a number of developmental, metabolic, and neural activities throughout the body. The thyroid gland synthesizes 2 hormones. The 2 main hormones secreted by the thyroid gland are thyroxine, which contains 4 atoms of iodine (T4), and triiodothyronine (T3). T3 production in the thyroid gland constitutes approximately 20% of the total T3; the rest is generated by the conversion (deiodination) of T4 to T3 is also produced by conversion (deiodination) of T4 in peripheral tissues. Circulating levels of T4 are much greater than T3 levels, but T3 is biologically the most metabolically active hormone (3-4 times more potent than T4) although its effect is briefer due to its shorter half-life compared to T4.

 

Thyroid hormones circulate primarily bound to carrier proteins (eg, thyroid-binding globulin: TBG, prealbumin, and albumin); whereas only a small fraction circulates unbound (free). Only the free forms are metabolically active. While both T3 and T4 are bound to TBG, T3 is bound less firmly than T4. Total T3 consists of both the bound and unbound fractions.

 

In hyperthyroidism, both T4 and T3 levels are usually elevated, but in a small subset of hyperthyroid patients, only T3 is elevated (T3 toxicosis).

 

In hypothyroidism T4 and T3 levels are decreased. T3 levels are frequently low in sick or hospitalized euthyroid patients.

 

See Thyroid Function Ordering Algorithm in Special Instructions.

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Pediatric

0-5 days: 73-288 ng/dL

6 days-2 months: 80-275 ng/dL

3-11 months: 86-265 ng/dL

1-5 years: 92-248 ng/dL

6-10 years: 93-231 ng/dL

11-19 years: 91-218 ng/dL

 

Adult (> or =20 years): 80-200 ng/dL

 

For SI unit Reference Values, see www.mayocliniclabs.com/order-tests/si-unit-conversion.html

Interpretation
Provides information to assist in interpretation of the test results

Triiodothyronine (T3) values above 200 ng/dL in adults or over age related cutoffs in children are consistent with hyperthyroidism or increased thyroid hormone-binding proteins.

 

Abnormal levels (high or low) of thyroid hormone-binding proteins (primarily albumin and thyroid-binding globulin) may cause abnormal T3 concentrations in euthyroid patients.

Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Triiodothyronine (T3) is not a reliable marker for hypothyroidism.

 

Therapy with amiodarone can lead to depressed T3 values.

 

Phenytoin, phenylbutazone, and salicylates cause release of T3 from the binding proteins, thus leading to a reduction in the total T3 hormone level at normal free T3 levels.

 

Autoantibodies to thyroid hormones can interfere with the assay.

 

Binding protein anomalies may cause values that deviate from the expected results. Pathological concentrations of binding proteins can lead to results outside the reference range, although the patient may be in a euthyroid state. Free T3 or free T4 testing is indicated in these cases.

 

Some patients who have been exposed to animal antigens, either in the environment or as part of treatment or imaging procedures, may have circulating anti-animal antibodies present. These antibodies may interfere with the assay reagents to produce unreliable results.

 

T3 has a 15-fold higher affinity for thyroid receptor compared to T4.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Hay ID, Klee GG: Linking medical needs and performance goals: clinical and laboratory perspectives on thyroid disease. Clin Chem. 1993;39:1519-1524

2. Klee GG: Clinical usage recommendations and analytic performance goals for total and free triiodothyronine measurements. Clin Chem. 1996;42:155-159

3. Freedman DB, Halsall D, Marshall WJ, Ellervik C: Thyroid disorders. In: Rifai N, Horvath AR, Wittwer CT: eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018:1572-1616

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Description
Describes how the test is performed and provides a method-specific reference

The Roche triiodothyronine assay (T3) is a competitive assay using electrochemiluminescence detection. Bound T3 is released from binding proteins by 8-anilino-1-naphthalene sulfonic acid (ANS). The patient specimen is incubated with a sheep polyclonal anti-T3 antibody labeled with ruthenium. Streptavidin-coated microparticles and biotinylated T3 are added for a second incubation during which the still free binding sites of the labeled antibody become occupied. The resulting immunocomplex becomes bound to the solid phase by interaction of biotin and streptavidin. The reaction mixture is aspirated into the measuring cell where the microparticles are magnetically captured onto the surface of the electrode. Unbound substances are removed and application of a voltage to the electrode induces the electrochemiluminescent emission. This signal is measured against a calibration curve to determine patient results.(Package insert: Roche cobas. Roche Diagnostics; 08/2019)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information

No

Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Friday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

1 to 3 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

14 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test

Rochester

Fees
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

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
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.

84480

LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
T3 T3 (Triiodothyronine), Total, S 83124-8
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
T3 T3 (Triiodothyronine), Total, S 83124-8

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Create a PDF

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports