Gene screening of 23 Japanese families with complete thyroxine-binding globulin deficiency: identification of a nucleotide deletion at codon 352 as a common cause.

Thyroxine-binding globulin (TBG) is a major thyroid hormone transport protein in human serum. Its complete deficiency (TBG-CD) is one of inherited TBG abnormalities that transmit on X-chromosome. We previously reported a nucleotide deletion at codon 352 of the TBG gene (TBG-CDJ) in Japanese families with TBG-CD. To determine the prevalence of this mutation in Japanese with TBG-CD, 23 affected subjects (19 males and 4 females) belonging to unrelated families living in 4 major islands of Japan were analyzed with regard to the mutation at codon 352. Their genomic DNAs were amplified by the polymerase chain reaction with allele specific primers. Nineteen male and four female subjects were shown to have the mutation as hemizygotes and heterozygotes, respectively. It is concluded that TBG-CDJ may be a common cause of TBG-CD in Japanese and might have appeared in the ancestors of the Japanese after the human race divergence.