ESPE Abstracts

Background: Partial thyroxine-binding globulin deficiency (TBG-PD) is an endocrine defect with a prevalence of 1:4 000 in newborns. Due to the presence of a single TBG gene on the X chromosome.

Objective and hypotheses: To investigate the clinical characteristics of twins with thyroxine binding globulin deficiency and to find SERPINA7 gene mutations.

Method: Data related to clinical characteristics, serum biochemistry, gene mutations and pedigree of two children with TBG deficiency were collected, the related literatures searched form China National Knowledge Infrastructure, Wanfang Data Knowledge Service Platform, National Center for Biotechnology Information and PubMed (up to December 2015) by using search terms “Thyroxine binding globulin deficiency, gene, mutation”.

Results: Both patients were diagnosed as central hypothyroidism at beginning and treated with L-thyroxine. Both of the identical twins of the triplet were observed mutation in exon3, c.631G>A(p.A211T), a new mutation had not been reported, but their parents and another non-identical triplet brother were normal. Literatures reviewed showed that 23 foreign cases with SERPINA7 gene mutation had been reported. Among reported that SERPINA7 gene mutations located in exon, intron, promoter and enhancer. Up to now, there were 49 variants had been identified, 41 of them located to the mutated genes. Including this two cases, patients with thyroxine binding globulin deficiency is characterized by reduced serum TH levels, but normal free TH and TSH and absent clinical manifestations.

Conclusion: The new mutation of SERPINA7 gene c.631G>A(p.A211T) is not transmit with the known X chromosome linked heredity, and as the cases were test tube triplet babies, we speculated it was a de novo mutation. The serum thyroid function test of TBG deficiency manifested as the decreased TT4, TT3 and normal TSH. And often misdiagnose as central hypothyroidism.No medicine should be taken to patient with TBG deficient and the only thing we should do is observation and follow-up.