Clinical Snapshot
Biotin Interference in Thyroid Function Tests
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A 40-year-old female patient with kidney disease requiring dialysis developed abnormal thyroid values following the resolution of subacute thyroiditis (De Quervain’s thyroiditis): slightly elevated TSH (5.8 mIU/l) and significantly elevated fT4 (61 pmol/l) and fT3 (12 pmol/l). Clinically, the patient was euthyroid, which presumably delayed the further diagnostic work-up. The abnormal constellation of laboratory values was caused by the patient’s self-initiated, daily use of high-dose biotin (10 mg) to treat hair loss (telogen effluvium) following the hypothyroid phase of thyroiditis. Biotin interferes with biotin-streptavidin-based immunoassays and can cause falsely high free thyroid hormone levels. Following discontinuation of biotin, laboratory values normalized fully. Biotin preparations are widely used and available over the counter even in high doses; however, their potential to interfere with biotin-based immunoassays (producing both falsely high results in the case of competitive assays, as described here for fT3 and fT4, and falsely low results in sandwich assays, such as troponin and TSH) is often overlooked. In the case of unexplained constellations of thyroid values, especially when those do not correlate with the clinical presentation, patients should be specifically asked about biotin use and advised to pause use before re-testing in order to avoid inappropriate diagnostic and therapeutic measures.
Dr. med. Martin Rußwurm, PD Dr. med. Johannes Wild, Zentrum für Innere Medizin, Schwerpunkt Nephrologie, Transplantationsmedizin und internistische Intenisvmedizin, martin.russwurm@staff.uni-marburg.de
Dr. med. Joachim Göbel, Zentrum für Innere Medizin, Schwerpunkt Gastroenterologie, Endokrinologie, Stoffwechsel und klinische Infektiologie
Conflict of interest statement: The authors state that no conflict of interest exists.
Translated from the original German by Christine Rye.
Cite this as: Russwurm M, Göbel J, Wild J: Biotin interference in thyroid function tests. Dtsch Arztebl Int 2025; 122: 557. DOI: 10.3238/arztebl.m2025.0114
