Mass screening for complete deficiency of thyroxine-binding globulin in adult Japanese by comprehensive health examination.

The incidence of complete thyroxine-binding globulin (TBG) deficiency (TBG-CD) was determined for a Japanese population from a comprehensive health examination, in which a T3 resin uptake test of the upper 5% (78 subjects from among 1,589 men) was the screening line for TBG-CD. Further analysis of the known mutation in TBG-CD gene of the Japanese population (reported as TBG-CDJ with codon 352 deletion) was performed on 72 subjects, and three were found to have TBG-CDJ, two of whom were siblings. Only those three subjects had a serum TBG concentration of less than 5 mg/l. The six subjects for whom the DNA analysis was not performed, did not have a serum TBG level of less than 5 mg/l. From these findings, the gene frequency of TBG-CDJ was calculated to be 0.13%. The incidence of TBG-CDJ in the total Japanese population is suggested to be 0.09%.