Application of 131I- and 125I-thyroxine in research of thyroid activity control

A report is presented on determining the normal levels of free thyroxine and triiodothyronine in the blood sera of man and of animals using tracer techniques with 125I as a tracer. A method was elaborated of determining thyroxine by equilibrium dialysis and conditions were found of the quantitative chemical analysis of the blood sera of man and of rats for triiodothyronine. A nodification of the method made possible microanalysis of samples smaller than 2 ml, thus permitting the application of the procedure in determining the components in the blood serum of individuals in contrast to the previous practice when only mixtures of blood sera taken from groups of animals could be analyzed. The effect was also studied of certain significant factors, such as anaesthetics and others on the level of free thyroxine in the blood sera of man and of rats. (L.O.)