Circulating Antibodies to T4 Causing Discordant Tests of Thyroid Function: A Case Report

ABSTRACT

The presence of elevated free thyroxine (fT4) hormone level with non-suppressed thyroid-stimulating hormone (TSH) level is called as “inappropriate secretion of TSH’’. TSH-secreting adenoma, resistance to thyroid hormone (RTH), iodothyronine deiodinase defect or false elevation of measured free serum T4 as in familial dysalbuminemic hyperthyroxinemia (FDH) and the presence of autoantibodies to T4 may be the cause of this entity. We report a case that presented with high serum fT4 and TSH levels associated with autoantibodies to T4.