Title: Technical aspects of the estimation of triiodothyronine in human serum: Evidence of conversion of thyroxine to triiodothyronine during assay
Abstract: The method of Sterling et al. for measuring triiodothyronine in human serum has been modified to provide greater sensitivity. The changes in technique include greater separation of triiodothyronine from thyroxine during paper chromatography, quantitation of triiodothyronine using a more dilute binding-protein solution, and the use of modifications which minimize the artifacts due to unknown substances in the chromatography paper. Complete recovery is obtained of known quantities of triiodothyronine added to human serum in amounts of 0.7 to 4.7 ng/ml. Mean triiodothyronine concentrations in human serum using this method are 1.8 ± 0.4 (SD) in normals, 6.7 ± 3.3 (SD) in untreated hyperthyroid subjects, and 0.66 ± 0.39 (SD) in hypothyroid patients. These values are 18 to 30% lower than those previously reported. We have examined the influence of thyroxine on the determination of triiodothyronine using both labeled and unlabeled hormone. The results suggest that about 0.3 to 0.4% of the total thyroxine present in serum is deiodinated to triiodothyronine. This appears to occur during the paper chromatographic step. Because of these observations, it would appear that the modified method, while quite satisfactory for clinical purposes, does not as yet provide the sensitivity and precision required for studies of triiodothyronine kinetics.
Publication Year: 1971
Publication Date: 1971-06-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 43
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