THE ROLE OF THYRONINE IN THYROID HORMONE METABOLISM

Abstract
Thyronine (TO) has been identified in human urine using gas chromatography-mass fragmentography (G.C.M.F.). In 22 normal individuals urinary TO concentration was found to range between 8-25 nmol⁄24h. Assuming the mean normal thyroxine (T4) production rate to be approximately 100 nmol⁄24h, our findings indicate that less than 20% of this could be accounted for as urinary TO excretion, thus supporting earlier findings that the peripheral metabolism of T4 is not limited solely to deiodination.