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HelpOrder Code RT3 T3 (Triiodothyronine), Reverse, Serum
Additional Codes
Epic Order ID LAB3052
Reporting Name
T3 (Triiodothyronine), Reverse, SUseful For
Aiding in the diagnosis of the sick euthyroid syndrome
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
SerumSpecimen Required
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube:
Preferred: Red top
Acceptable: Serum gel
Submission Container/Tube: Plastic vial
Specimen Volume: 0.8 mL
Collection Instructions: Centrifuge and aliquot serum into a plastic vial.
Specimen Minimum Volume
0.4 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Refrigerated (preferred) | 28 days | |
| Ambient | 28 days | ||
| Frozen | 28 days |
Reference Values
10-24 ng/dL
Day(s) Performed
Monday through Friday
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
84482
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| RT3 | T3 (Triiodothyronine), Reverse, S | 3052-8 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 9405 | T3(Triiodothyronine),Reverse,S | 3052-8 |
Clinical Information
Reverse triiodothyronine (rT3) differs from triiodothyronine (T3) in the positions of the iodine atoms attached to the aromatic rings. The majority of rT3 found in the circulation is formed by peripheral deiodination (removal of an iodine atom) of T4 (thyroxine). rT3 is believed to be metabolically inactive.
The rT3 level tends to follow the T4 level: low in hypothyroidism and high in hyperthyroidism. Additionally, increased levels of rT3 have been observed in starvation, anorexia nervosa, severe trauma and hemorrhagic shock, hepatic dysfunction, postoperative states, severe infection, and in burn patients (ie, sick euthyroid syndrome). This appears to be the result of a switchover in deiodination functions with the conversion of T4 to rT3 being favored over the production of T3.
Clinical Reference
1. Bowerbank SL, Carlin MG, Dean JR. A direct comparison of liquid chromatography-mass spectrometry with clinical routine testing immunoassay methods for the detection and quantification of thyroid hormones in blood serum. Anal Bioanal Chem. 2019;411(13):2839-2853
2. Moore WT, Eastman RC: Diagnostic Endocrinology. Mosby; 1990:182-183
Report Available
2 to 6 daysReject Due To
| Gross hemolysis | Reject |
| Gross lipemia | OK |
| Gross icterus | OK |
Method Name
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
Portions of this test are covered by patents held by Quest Diagnostics.
Forms
If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:
-General Request (T239)
-Renal Diagnostics Test Request (T830)