Misdiagnosis of Graves’ hyperthyroidism due to therapeutic biotin intervention

Abstract Background: Lately, high dose of biotin is often given orally to patients with a primary progressive multiple sclerosis (PPMS). However, the molecule biotin is also a principle compound in various analytic immunoassays. Clinical case: An asymptomatic 60-year-old woman with PPMS on high dose of biotin therapy (3 × 100 mg/d) displayed abnormal thyroid function tests (TSH 0.02 mU/l, fT4 > 103 pmol/l, and fT3 > 46 pmol/l). TSH was determined by a homogeneous sandwich chemiluminescent immunoassay and fT4 and fT3 were both determined by a homogeneous, sequential, chemiluminescent immunoassay. TSH receptor antibodies were found to be markedly elevated (>40 IU/l) using a electrochemiluminescence immunoassay, suggestive for Graves’ hyperthyroidism. Due to inconsistency between clinical presentation and laboratory results, thyroid function tests have been repeated with two other immunoassays. A direct, labeled antibody, competitive immunoassay to determine TSH and a luminescent immunometric immunoassay to ...