Radioimmunoassay for serum thyroxine-binding globulin: results in normal subjects and in patients with hepatocellular carcinoma.

Serum thyroxine-binding globulin (TBG) was measured by radioimmunoassay. The human TBG used in this study was purified by affinity, anion-exchange, and gel filtration chromatography. The serum TBG concentration in 98 euthyroid normals was 1.48 +/- 0.46 mg/100 ml (mean +/- SD), which is one-half that previously reported using a similar method. The level in females (1.66 +/- 0.56) was significantly higher than that in males (1.37 +/- 0.37). Comparison of the serum TBG level and the maximum binding capacity of serum TBG for thyroxine (T4) yielded a molar ratio of 1:1 for T4 and TBG. The mean serum TBG in 19 patients with hepatocellular carcinoma was 2.10 +/- 1.29 mg/100 ml; however, only 2 of these patients had serum TBG levels outside the normal range.