Diagnosis of thyroid hormone transport protein anomalies: an overview.

Inherited or acquired variations in the serum concentrations of TBG, TTR or albumin are rather common. Clinical studies have shown that most patients with transport protein variations were referred for thyroid testing because of incidentally detected "unusual" thyroid function tests. Although, usually no palpable thyroid abnormalities were found, the interpretation of these unexpected thyroid function tests resulted very often in inappropriate treatment with surgery, 131-iodine, antithyroid drugs as well as T4-replacement therapy. The clinical impact in the interpretation and diagnosis of thyroid hormone transport protein variations is to prevent these patients of unnecessary and sometimes also contraindicated treatment. If changes in thyroid hormone transport proteins in individuals with thyroid disorders or in individuals with the coexistence of two inherited defects are seen, difficulties in the interpretation of thyroid function tests will still occur.