Erroneous thyroid diagnosis due to over-the-counter biotin

Area of Science:

• Biochemistry
• Endocrinology
• Clinical Diagnostics

Background:

• Biotin, a B-complex vitamin, is crucial for immunoassays detecting hormones like thyrotropin (TSH) and thyroxine.
• The streptavidin-biotin bond is vital for analyte anchoring in these diagnostic tests.

Observation:

• Over-the-counter (OTC) biotin use, even in dietary supplements, can interfere with biotin-streptavidin-based immunoassays.
• Four cases illustrate how OTC biotin led to misdiagnoses and clinical confusion in patients with thyroid disease.

Findings:

• Exogenous biotin, at levels found in OTC products, can spuriously lower TSH measurements.
• This interference affects the accurate diagnosis of thyroid disorders.

Implications:

• Widespread OTC biotin use for cosmetic and health reasons poses a risk to accurate thyroid function testing.
• Clinicians must routinely question patients about biotin supplementation before thyroid testing to prevent diagnostic errors.