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Thyroxine-binding globulin deficiency in early childhood. Postnatal changes in serum concentrations of thyroid
Insights
Thyroid hormone-binding globulin (TBG) deficiency was observed in a euthyroid infant and her mother. Despite low total thyroid hormones, free hormone levels and TSH remained normal, suggesting TBG deficiency does not impair thyroid hormone status in this case.
Area of Science:
- Endocrinology
- Genetics
- Biochemistry
Background:
- Thyroid hormone-binding globulin (TBG) is crucial for thyroid hormone transport.
- TBG deficiency is a rare genetic condition affecting thyroid hormone levels.
- Understanding TBG deficiency is important for accurate thyroid function assessment.
Purpose of the Study:
- To investigate thyroid hormone profiles in a euthyroid infant and her mother with TBG deficiency.
- To assess the impact of TBG deficiency on free and total thyroid hormone levels.
- To explore the inheritance pattern of TBG deficiency within the family.
Main Methods:
- Serial measurements of serum T4, T3, TSH, TBG, TBPA, and albumin.
- Analysis of thyroid hormone parameters over 22 months post-delivery.
- Family pedigree analysis to suggest inheritance pattern.
Main Results:
- The infant presented with TBG levels around 50% of normal, which persisted through infancy.
- Total serum T4 and T3 were low, but free T4, free T3, and TSH levels were normal in the child.
- The mother, with a history of thyroid hormone therapy, also showed TBG deficiency post-partum, remaining euthyroid after treatment withdrawal.
Conclusions:
- Congenital TBG deficiency in an infant does not necessarily lead to hypothyroidism.
- TBG deficiency can be inherited, with X-linked inheritance suggested in this family.
- Normal free thyroid hormone levels and TSH indicate euthyroidism despite low total T4 and T3.
Abstract:
Serial determinations of serum thyroxine (T4), triiodothyronine (T3), thyrotropin (TSH), thyroid hormone-binding globulin (TBG), prealbumin (TBPA) and albumin were performed in a euthyroid girl with TBG deficiency and in her mother for a period of 22 months after delivery. At 8 days old the child had a serum TBG concentration around 50% of normal level which remained essentially unchanged during infancy. Total serum T4 and T3 concentrations were low, the free serum T4, free serum T3 and serum TSH concentrations were normal. The mother had received thyroid hormone from the age of 15 years. Her serum TBG level at 6 weeks post partum was similar to that of non-pregnant adults but decreased to about 50% of normal level, indicating a TBG deficiency. She remained euthyroid after withdrawal of T4 therapy. Serum TBPA and albumin concentration were normal in mother and child. An X-linked inheritance of the TBG deficiency was suggested from a study of the family.