Conversion of Thyroxine to Triiodothyronine in Normal Human Subjects

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Science  11 Sep 1970:
Vol. 169, Issue 3950, pp. 1099-1100
DOI: 10.1126/science.169.3950.1099


The conversion of thyroxine to triiodothyronine, previously demonstrated in athyreotic human subjects, has been investigated in normal subjects who were given intravenous injections of purified thyroxine labeled with carbon-14 in ring A and in the alanine side chain. Evidence for the conversion of T4 to T3 was provided by the finding of carbon-14 in the T3 fraction isolated from serums. It is estimated that an appreciable fraction of T4 may be transformed to T3 in normal man.

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