3,3'-Diiodothyronine concentrations in hospitalized or thyroidectomized patients: results from a pilot study. 

 -  2014 
<br/><br/> CONCLUSION: We observed associations between inpatient status and reduced 3,3'-T2 concentrations. This appears to be a global change associated with illness, rather than an association with specific medical conditions. We also observed higher 3,3'-T2 concentrations in athyreotic outpatients receiving thyroid-stimulating hormone (TSH) suppression therapy. This demonstrates that there is production of 3,3'-T2 from levothyroxine (LT4) in extrathyroidal tissues. Conversion of thyroxine (T4) to 3,3'-T2 via both triiodothyronine (T3) and reverse triiodothyronine (rT3) pathways may prevent excessive T3 concentrations in such patients.  METHODS: A total of 100 patients who were recruited from a group of inpatients and outpatients with a diverse range of medical conditions, donated a single blood sample that was assayed for thyroid hormone derivatives using liquid-chromatography tandem mass spectrometry (LC-MS/MS). The associations between 3,3'-T2 concentrations and physiologic data and medical conditions were assessed.  OBJECTIVE: To determine if various medical conditions affect the serum concentrations of 3,3'-diiodothyronine (3,3'-T2).  RESULTS: Higher quartiles of 3,3'-T2 concentrations (quartile 1: 2.01-7.48, quartile 2: 7.74-12.4, quartile 3: 12.5-17, quartile 4: 17.9-45.8 pg/mL) were associated with decreasing occurrence of critical illness (58%, 11%, 0%, 8%), stroke (29%, 7.7%, 4%, 0%), critical care unit hospitalization (75%, 39%, 8.3 %, 12%), and inpatient status (83%, 42%, 8%, 12%) (all P<.001). The same quartiles were associated with increasing frequency of thyroidectomy (4%, 12%, 17%, 60%). In multivariate analyses, after adjustment for age and sex, inpatient status was associated with decreasing concentrations of 3,3'-T2 (46% decrease for inpatients with 95% confidence interval [CI] 32-57%, P<.0001). Thyroidectomy was associated with increasing concentrations of 3,3'-T2 (29% increase (CI 0.5-66%, P = .049). 
<br/><br/><br/>English 
<br/><br/><label>ISSN: </label>1530-891X 
<br/><br/><label>Subjects--Topical Terms: </label><br/>*Diiodothyronines/bl [Blood]<br/>*Thyroidectomy<br/>Adult<br/>Aged<br/>Female<br/>Hospitalization<br/>Humans<br/>Male<br/>Middle Aged<br/>Pilot Projects<br/>Tandem Mass Spectrometry<br/>Triiodothyronine/bl [Blood]
<br/><br/><label>Subjects--Geographic Terms: </label><br/>MedStar Health Research Institute<br/>MedStar Washington Hospital Center
<br/><br/><label>Index Terms--Occupation: </label><br/>Medicine/Endocrinology
<br/><br/><label>Index Terms--Function: </label><br/>Journal Article<br/>Research Support, N.I.H., Extramural