BACKGROUND
Biotin is a dietary supplement that belongs to vitamin B family. Although not proven, large doses of biotin are taken by some for purposes like improving hair and nail quality. Further, some skin doctors also recommend biotin for these issues. Biotin has no effect on thyroid hormone levels or thyroid function in the body. However, biotin can interfere with the measurement of hormone levels in the laboratory, making them inaccurate. This is because biotin is added as a reagent during some of the laboratory methods. The hormone measurements that can be affected are thyroxine, triiodothyronine, TSH and thyroglobulin. This effect may falsely change the results and lead to an incorrect diagnosis. Precise measurement of thyroid hormones and TSH is important for diagnosis of thyroid disorders. Similarly, an accurate testing of thyroglobulin is vital for patients with thyroid cancer, as it can serve as a cancer marker.

This study has been done to compare the effect of biotin intake on hormone levels from 4 different laboratories used in diagnosis of thyroid disorders. Biotin is added as a reagent in the assays from Roche and Siemens but is not used in the assays from Abbot or when done using mass spectrography (LC-MS/MS).

THE FULL ARTICLE TITLE
Ylli D et al 2021 Biotin interference in assays for thyroid hormones, thyrotropin and thyroglobulin. Thyroid 31:1160–1170. PMID: 34042535.

SUMMARY OF THE STUDY
The authors recruited 13 volunteers to participate in the study; 9 women and 4 men with an average age of 45 years (range: 28-67). Of the participants, 10 had no thyroid disease and 3 had prior thyroid surgery and had to take Levothyroxine on daily basis.

All had normal levels of thyroid hormone, TSH and thyroglobulin at the time of study. They were asked to take 10,000 mcg of biotin daily for 8 days. Blood tests were done before and in 2 and 5 hours after taking biotin on day 1 and day 8. Thyroid hormones were measured by Roche Cobas 6000, Abbott architect and LC-MS/MS and thyroglobulin was measured by Siemens Immulite 2000. Their levels were compared on day 1 and day 8, before and after taking Biotin.

A significant decrease in TSH and significant increases in FT4 and TT3 concentrations were observed between baseline at day 1 and all time points but baseline at day 8 after taking biotin when Roche Cobas 6000 was used. Thyroglobulin levels were found to be falsely lower after taking biotin with the Siemens Immulite 2000 assay. No change in hormone levels were noted after biotin when measured by the Abbott assay or the LC-MS/MS, although the TSH was falsely lower 2 h after taking biotin with the Abbott assay.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study shows that taking a 10,000 mcg daily dose of Biotin (a commonly used dose) may falsely change the result of the blood test for TSH, Free T4, total T3 and thyroglobulin. This change does not happen with all types of laboratory methods; it mostly occurs when biotin is used in the process of hormone measurement. Additional factors like, the dose of biotin and the time of the blood test from intake of biotin are also important. Patients and clinicians should be aware of this effect. In general, patients taking biotin should stop the supplement for at least 3-5 days before getting thyroid levels tested.

— Shirin Haddady, MD, MPH

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