A Case of Hypothyroxinemia with Thyroxine-Binding-Globulin Deficiency

ABSTRACT

The transport proteins such as thyroxine-binding-globulin (TBG), albumin and transthyretin carry over 99% of circulating thyroid hormones. TBG is a major thyroid hormone transport protein in serum. Although TBG deficiency does not have metabolic consequences, it has diagnostic implications as it can lead to an incorrect interpretation of thyroid function tests. We experienced a case that a man who had an abnormal thyroid function showed unexpectedly low concentrations of serum total thyroxine. We detected the low TBG in his serum and he was diagnosed the TBG deficiency. We report this case along with a review of the related literature.