Comparison of Biological and Chemical Assay of Thyroid

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Abstract
The biological and chemical examination of thyroid samples has demonstrated the inadequacy of the B.P. assay, which is based upon the determination of so-called “thyroxine iodine”. It is suggested that, in the absence of specific methods for determining thyroxine and tri-iodothyronine in thyroid, the chemical assay should be replaced by a biological assay. The mouse anoxia method is shown to be suitable for this purpose. The potencies of samples assayed thus over the past 3 years, together with chemical data and clinical comments are presented. The relative activities of the thyroid constituents 3,5,3′,5′-tetra-iodo-L-thyronine (L-thyroxine), 3,5,3′-tri-iodo-L-thyronine, 3,5-di-iodo-L-tyrosine, 3-mono-iodo-L-tyrosine, as determined by the mouse anoxia method, are in good agreement with their reported clinical effectiveness.