Inherited thyroxine-binding globulin deficiency
Inherited thyroxine-binding globulin deficiency is a genetic condition that reduces the amount of a specific protein in the blood but typically does not cause health problems.
Overview
Inherited thyroxine-binding globulin deficiency is a genetic condition that typically does not cause health problems. Thyroxine-binding globulin is one of three major proteins in the bloodstream that carries hormones made by the thyroid gland. Thyroid hormones are essential for regulating growth, brain development, and metabolism.
A shortage (deficiency) of this protein reduces the total amount of thyroxine in the blood. While the condition does not usually affect thyroid function, it is often identified during bloodwork performed to rule out other conditions. It is important to diagnose this correctly to avoid confusion with more serious disorders, such as hypothyroidism, and to prevent unnecessary treatments.
Forms
- Partial form: Reduces the amount of functioning thyroxine-binding globulin. This is the most common form, occurring in approximately 1 in 4,000 infants.
- Complete form: Causes a more significant loss of functioning thyroxine-binding globulin.
Causes
Variants in the SERPINA7 gene cause the inherited form of this deficiency. These variants may lead to a shortened, non-functional protein or change a single amino acid, reducing the amount of protein available to bind to thyroid hormones.
Some cases are acquired during a person’s lifetime rather than inherited. Causes of acquired deficiency include malnutrition, kidney disease, liver disease, increased levels of male sex hormones (androgens), or as a side effect of certain medications.
Inheritance
This condition is inherited in an X-linked pattern. In males, who have only one X chromosome, a variant in the only copy of the gene is sufficient to cause the condition. In females, who have two copies of the X chromosome, one altered copy may reduce protein levels, but these individuals often maintain levels within the normal range. Fathers cannot pass X-linked traits to their sons.