Thyroid hormone binding ratio

Indications

Examples

• In patients with hyperthyroidism, there will be fewer available binding sites on TBG. This will lead to an increased Thyroid Hormone Binding Ratio.
• In patients with hypothyroidism, there will be more free binding sites on TBG and as such the THBR will be decreased.
• In general, High with High thyroid activity and Low with Low thyroid activity.

  Other Conditions

• Total TBG can be increased congenitally, or in conditions such as pregnancy and with the treatment of certain infections such as Hepatitis C. In the latter, reduction of inflammation of the liver results in increased protein synthesis
• Total TBG can be decreased congenitally, or in conditions such as liver failure, protein-losing conditions, or Nephrotic conditions. Increased androgen levels will also decrease TBG synthesis, increasing THBR.
• THBR can be directly altered by drugs such as;
• * Anticonvulsants such as Phenytoin and Carbamazepine
• * Antinflammatory drugs such as Salicylates or Phenylbutazone
• * High levels of Free Fatty Acids, commonly seen in acutely ill patients.

  Limitations