• Clinical and Experimental Pediatrics
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• v.45 no.6
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• pp.796-799
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• 2002

A child diagnosed with congenital hypothyroidism after newborn screening and follow up thyroid function test at 1 month of life in another general hospital demonstrated euthyroid state with thyroxine( $T_4$) supplementation until the age of 22 months of life, when he was transferred to our hospital, where he was diagnosed as thyroxine binding globulin(TBG) deficiency with low $T_4$ and TBG. Withdrawal of $T_4$ at age of 26 months was associated with hyperthyrotropinemic hypothyroidism. This patient is a case of TBG deficiency associated with hypothyroidism, and in rare instances, TBG deficiency may lead to hypothyroidism requiring hormone supplementation.

• Clinical and Experimental Pediatrics
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• v.48 no.11
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• pp.1252-1255
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• 2005

Abnormalities in the levels of thyroxine-binding globulin (TBG) are not associated with clinical disease and they do not require treatment. Congenital TBG deficiency is inherited in an X-linked manner. To date, some complete and partial TBG variants and one polymorphism have been identified by analysis of the TBG gene. Two male neonates were referred to us because of their low $T_4$ levels that were noted on the neonatal screening test. They showed normal levels of free $T_4$ and TSH. Their serum TBG was not detectable and those values of their parents were within the normal ranges. The genomic DNA was extracted from their white blood cells and the four coding exons of the TBG gene were amplified by using polymerase chain reaction. Sequencing of the four coding regions and all the intron/exon junctions revealed a single nucleotide deletion of the first base of the codon 352 of the mature protein in both of the neonates. This mutation resulted in a frameshift and a premature stop codon (TGA) 374. Their mothers were shown to be heterozygotes. We detected a single nucleotide deletion resulting in a frameshift in two male Korean neonates who had complete TBG deficiency.