Partial Thyroid Hormone-Binding Globulin Deficiency: A Case Report and Literature Review

Area of Science:

• Endocrinology
• Genetics
• Molecular Biology

Background:

• Thyroxine binding globulin (TBG) deficiency is a rare inherited endocrine disorder.
• It is primarily caused by genetic mutations, often with X-linked recessive inheritance patterns.
• Understanding TBG deficiency is crucial for accurate thyroid function assessment.

Purpose of the Study:

• To summarize the clinical features of children with TBG deficiency and their families.
• To analyze Serpina7 gene mutations in TBG deficiency.
• To provide a reference for differentiating TBG deficiency.

Main Methods:

• Thyroid function tests were conducted on TBG-deficient patients.
• Genetic analysis involved polymerase chain reaction (PCR) and direct DNA sequencing of the Serpina7 gene.
• A literature search was performed using keywords related to TBG, genes, and mutations.

Main Results:

• Patients exhibited low TBG, triiodothyronine (T3), and thyroxine (T4) levels, with normal thyrotropin (TSH), free T3 (FT3), and free T4 (FT4), indicating partial TBG deficiency.
• A missense mutation (C.909 g > T) in exon 4 of the Serpina7 gene was identified in the patient and father.
• Literature review identified 45 studies detailing 49 variants of the Serpina7 gene, predominantly in exons.

Conclusions:

• The identified Serpina7 C.909G (P.L303F) mutation is inherited in an X-linked recessive manner.
• Key clinical features of TBG deficiency include low serum T4, T3, and TBG levels with normal TSH, FT3, and FT4, often without overt clinical symptoms.