title: Diagnostic Dilemma in Discordant Thyroid Function Tests Due to Thyroid Hormone Autoantibodies.
abstract: OBJECTIVE
  Assay interference could be the cause of abnormal thyroid function tests. Early recognition prevents inappropriate patient management. The objective of this report is to present a case with discordant thyroid function tests in different thyroid assay platforms due to thyroid autoantibodies.
  
  
  METHODS
  We present a case her family, laboratory data and methods that investigate immunoassay interference.
  
  
  RESULTS
  A 21-year-old woman with autoimmune thyroid disease was treated for hypothyroidism with levothyroxine and noted to have elevated total and free thyroxine, free triiodothyronine but normal thyroid-stimulating hormone. Repeat thyroid function tests using different platforms revealed discrepant results. Further investigation showed that the patient had positive thyroid hormone autoantibodies (THAAbs).
  
  
  CONCLUSIONS
  We demonstrates abnormal thyroid function tests caused by THAAbs. The latter were the cause of interference with assays resulting in discrepant test results inconsistent with the clinical presentation. Early recognition would prevent inappropriate patient management.
authors.affiliation: Department of Medicine, The University of Chicago, Chicago, Illinois.
authors.forename: Panudda
authors.initials: P
authors.lastname: Srichomkwun
authors.affiliation: Department of Medicine, The University of Chicago, Chicago, Illinois.
authors.forename: Neal H
authors.initials: NH
authors.lastname: Scherberg
authors.affiliation: Department of Pediatrics, General Hospital, Sibenik, Croatia.
authors.forename: Jasminka
authors.initials: J
authors.lastname: Jakšić
authors.affiliation: Department of Medicine, The University of Chicago, Chicago, Illinois; Department of Pediatrics and the Committee on Genetics, The University of Chicago, Chicago, Illinois.
authors.forename: Samuel
authors.initials: S
authors.lastname: Refetoff
keywords: euthyroid hyperthyroxinemia; thyroid function test; thyroid hormone autoantibodies