Effect of Albumin Polymorphism on Thyroid Hormones: A Case Report and Literature Review.

Abstract

Familial dysalbuminemic hyperthyroxinemia (FDH) is the most common cause of the inherited increase of serum thyroxine in Caucasians. This disorder occurs due to a missense mutation in the human serum albumin, resulting in an increased affinity of thyroxine to the binding sites on the human serum albumin (HSA) molecule. HSA is a carrier protein of thyroid hormones and only 10% of thyroxine (T4) is bound to human serum albumin, 75% is bound to thyroxine-binding globulin, 15% to transthyretin, and 0.03% is free. The disorder is characterized by a greater elevation of serum thyroxine than triiodothyronine (T3). The high serum concentration of T4 is due to the modification of a binding site located in the N-terminal half of HSA (in subdomain IIA). Arg218 or Arg222 gets replaced with smaller amino acids, such as histidine, proline, or serine, due to missense mutation; this reduces the steric hindrances in the binding site and creates a high-affinity binding site for thyroxine. We herein report a case of FDH with a characteristically elevated total T4 and normal free T4 (measured by equilibrium dialysis).

• Authors: Rupak Mahendhar, Amir Shahbaz, Maria Riaz, Michael Aninyei, David M Reich, Issac Sachmechi
• Journal: Cureus (Cureus) Vol. 10 Issue 7 Pg. e2903 (Jul 01 2018) ISSN: 2168-8184 [Print] United States
• PMID: 30197844 (Publication Type: Case Reports)