First report of inherited thyroxine-binding globulin deficiency in Iran caused by a known de novo mutation in SERPINA7.

BACKGROUND

Thyroxine-binding globulin (TBG) is the main transporter of thyroid hormones in human serum, encoded by the gene TBG (SERPINA7), located in long arm of X-chromosome (Xq21-q22). Deficiency of SERPINA7 (serum protease inhibitor, clade A [alpha-1 antiproteinase, antitrypsin], member 7) leads to inherited TBG deficiency. Several mutations have been reported in the coding and noncoding regions of SERPINA7 in association with TGB deficiency.

METHODS

Automated chemiluminescence immunoassays were used to determine TSH, free and total T4 and T3 (fT4, TT4, TT3) and TBG. Direct DNA sequencing identified the mutation in SERPINA7.

RESULTS

We present a 3 and 4/12 year old boy, born premature, who was mismanaged as hypothyroidism before referral to our center, and was diagnosed with TBG deficiency at our center with a hemizygous substitution in exon 1, position c.347T > A, leading to replacement of isoleucine for arginine in position 96 (considering the first 20 amino acid signal peptide).

CONCLUSION

This known mutation, reported as the first SERPINA7 mutation in Iran, emphasizes the point that endocrinologists should pay more attention to inherited TBG to prevent unnecessary treatment.