Assay of thyroxine-binding globulin by polyacrylamide electrophoresis: normal values.

Thyroxine-binding globulin (TBG) assays by the polyacrylamide electrophoresis assay of Nikolai and Seal have been carried out on 315 normal subjects. The assay was carried out with 200 exogenous labeled thyroxine per 100 ml added to the samples. The means and standard deviations for the three thyroxine-binding proteins in males (n = 140) were: TBG 19.7 ±3.0 p.g/100 ml, thyroxine-binding albumin (TBA) 38.0 ± 10.3 J.g/100 ml, thyroxine-binding prealbumin (TBPA) 141.2 ± 10.9 z.g/ 100 ml. The values for females (n = 175) were: TBG 21.6 ± 3.2 .u.g/100 ml, TBA 40.0 ± 10 p.g/100 ml, 4nd TBPA 137 ± 10.5 i.g/100 ml. The difference in the means of the TBC values of males and females was significant (p < 0.01). Partial correlation analysis indicated that a significant correlation existed between proteinbound iodine and the TBG values only. A highly significant correlation was also found between the resin T3 uptake values and TBG. Persons (n = 43) receiving estrogens had a mean TBC of 36 p.g/100 ml with a range of 26-45. This is an elevation of almost 5 SDs above normal. The normal values obtained by the polyacrylamide assay are compared with other electrophoretic assays of TBG.