[Preliminary results of a new radioimmunoassay for thyroxine binding globulin (T.B.G.) (author's transl)].

A radioimmunoassay for the accurate measurement of T.B.G., developed by Crouzat-Reynes, was used to perform T.B.G. concentration in sera of euthyroid subjects in different clinical situations, in hypothyroid and hyperthyroid patients. In normal control, the T.B.G. concentration was not different from men and women, from young and old subjects (m = 21,1; sigma = 3,9). On the other hand, in women either pregnant (m = 51,2; sigma = 18,1) or receiving oral contraception (m = 30,1; sigma = 5,7), the T.B.G. levels were significantly higher than euthyro subjects. Cirrhosis of the liver and liver carcinoma were without apparent effect on T.B.G. levels because it was a too few number of patients and the group was too heterogeneous. In the group of hypothyroid (m = 25,9; sigma = 6,5) and hyperthyroid (m = 21,1; sigma = 5,5) patients, the T.B.G. serum concentrations were not significantly different from normal. The ratio T4/T.B.G., as I.T.L. (T4 X T3 uptake) permit to bring back in normal range T4 levels changed by extrathyroidal process; however, this ratio seems to us to be less interesting than standard I.T.L. The T.B.G. assay has not to be considered only as a substitution of T3 uptake because they do not study the same parameters.