Does biotin affect thyroid function tests?

Biotin Interference in Thyroid Function Tests

Biotin supplementation significantly interferes with thyroid function tests, causing falsely decreased TSH and falsely elevated T3/T4 levels that can mimic hyperthyroidism. 1

Mechanism of Interference

Biotin interference occurs due to the design of many laboratory immunoassays:

• Competitive assays: Biotin causes falsely elevated results (e.g., T3, T4)
• Sandwich assays: Biotin causes falsely decreased results (e.g., TSH) 1

This interference pattern creates laboratory results that can mimic hyperthyroidism (low TSH, high T4) in patients who are actually euthyroid, potentially leading to misdiagnosis and inappropriate treatment 2, 3.

Clinical Impact

The interference can affect multiple laboratory tests:

• Thyroid function tests (TSH, fT3, fT4)
• Thyroglobulin (Tg) measurements
• Parathyroid hormone (PTH) measurements 4
• Cardiac troponin tests (potentially missing myocardial infarction) 1

Dose and Timing Considerations

• Even moderate doses of biotin can cause interference
• A daily dose of 10mg has been shown to interfere with specific assays for TSH, fT4, TT3, and Tg 2
• Maximum interference occurs approximately 2 hours after biotin ingestion 2
• Laboratory values typically normalize within 24-48 hours after biotin withdrawal 5

Affected Assay Platforms

Different laboratory platforms have varying susceptibility to biotin interference:

• Roche Cobas 6000: Shows significant changes in TSH, fT4, and TT3 measurements after biotin exposure 2
• Siemens IMMULITE 2000: Shows falsely lower Tg levels 2
• Beckman DXI800: Shows positive interference with FT4, FT3, and total T3 assays but negative interference with thyroglobulin 6

Clinical Recognition Patterns

Suspect biotin interference when:

1. Laboratory results suggest hyperthyroidism but the patient has no clinical signs or symptoms 3, 7
2. There is discrepancy between total T3 (falsely elevated) and total T4 (normal if using non-biotin-based assay) 6
3. Laboratory abnormalities resolve rapidly after biotin discontinuation 7

Recommendations for Clinicians

1. Ask about supplement use specifically inquiring about biotin supplements, multivitamins, or hair/nail/skin supplements containing biotin 1

2. Advise patients to discontinue biotin at least 48-72 hours before thyroid function testing

3. Consider alternative assays when biotin interference is suspected:

   • Mass spectrometry-based methods
   • Immunoassays designed to be less susceptible to biotin interference 1

4. Communicate with the laboratory when clinical presentation doesn't match laboratory results 3

High-Risk Patient Groups

Be particularly vigilant with:

• Patients with multiple sclerosis (may be on high-dose biotin therapy)
• Patients with thyroid cancer requiring careful monitoring of thyroglobulin and TSH 2
• Patients using biotin for hair, skin, and nail health (often 5-10mg daily doses)

Conclusion

Biotin interference in laboratory testing is a significant clinical concern that can lead to misdiagnosis and inappropriate treatment. Clinicians should maintain a high index of suspicion when laboratory results don't match clinical presentation, especially in patients taking biotin supplements.