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Clear
 
Test Code:
090-31-4006

Order Name:
T3 (Triiodothyronine), Reverse, Serum **

 
Useful For:

An aid in the diagnosis of the "sick euthyroid" syndrome

 
Methodology:
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Portions of this test are covered by patents held by Quest Diagnostics.
 
AliasesName:
Reverse T3
 
 
 
Test Code:
090-31-4006

Order Name:
T3 (Triiodothyronine), Reverse, Serum **

 
Patient Preparation:
N/A
 
Collection Specimen Or Container:
Blood/ Plain blood (Red top) 6 mL, 2 tubes
 
Specimen Testing Type:
Serum, minimum volume 1 mL x 2 tubes
 
Sub Mission Container:
Plastic tube
 
Rejection Criteria:
Gross hemolysis Reject
Gross lipemia OK
Gross icterus OK
 
Specimen Stabillity:
Specimen Type Temperature Time
Serum Refrigerated, 2oC to 8oC (preferred) 28 days
Ambient 28 days
Frozen 28 days
 
 
 
Test Code:
090-31-4006

Order Name:
T3 (Triiodothyronine), Reverse, Serum **

 
Method detail:
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Portions of this test are covered by patents held by Quest Diagnostics.
 
Schedule:
N/A **Sent out to MAYO, USA
 
Turnaround Time:
Received specimen to report within 14 days
 
Performing Location:
MAYO Laboratory
Referral Lab Services, Laboratory Department 14160-2
 
 
 
Test Code:
090-31-4006

Order Name:
T3 (Triiodothyronine), Reverse, Serum **

 
 
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.

 
Reference Value:
10-24 ng/dL
 
Interpretation:
In hospitalized or sick patients with low triiodothyronine (T3) values, elevated reverse triiodothyronine (rT3) values are consistent with "sick euthyroid" syndrome. Also, the finding on an elevated rT3 level in a critically ill patient helps exclude a diagnosis of hypothyroidism.

The rT3 is high in patients on medications such as propylthiouracil, ipodate, propranolol, amiodarone, dexamethasone, and the anesthetic agent halothane. Dilantin decreases rT3 due to the displacement from thyroxine-binding globulin, which causes increased rT3 clearance.

To convert from ng/dL to nmol/L, multiply the ng/dL result by 0.01536.

Cautions:
Generally, reverse triiodothyronine tests are not necessary since triiodothyronine should not be ordered in hospitalized or sick patients.
 
Clinical Reference:
www.mayomedicallaboratories.com (Retrieved: 31 Jul 2020)