THEIN VIVOCONVERSION OF THYROXINE TO 3:5:3′-TRIIODOTHYRONINE

Abstract

Using descending paper chromatography in a solvent system which provides excellent separation of T4 and T3, we were unable to confirm previous work from this laboratory suggesting that T3 appears in the blood as the result of the extrathyroidal degradation of T4. This is not to suggest that degradation of T4 to T3 in extrathyroidal tissues does not occur. Our results indicate only that the T3 normally present in the circulating plasma is not a deiodination product of circulating T4.