Effect of High-dose Biotin on Thyroid Function Tests: Case Report and Literature Review

Biotin is a readily available supplement that is part of the B-complex vitamins. It is an essential co-factor for five carboxylases involved in fatty acid synthesis and energy production. The recommended daily intake (RDI) of biotin ranges from 30 to 70 mcg per day. At high doses (10,000 times RDI), biotin improves clinical outcomes and quality of life in patients with progressive multiple sclerosis (MS). It has been reported to cause interference in immunoassays resulting in abnormal thyroid function tests. Hereby we are describing the case of a patient having MS who was on high-dose biotin, seen in the clinic for a follow-up visit with thyroid function tests suggestive of Graves' disease with no signs and symptoms of hyperthyroidism and completely normal physical examination. In the case we have described, the laboratory measurements suggestive of thyrotoxicosis were attributed to interference of the patient's high-dose biotin treatment with the biotin-streptavidin chemistry of the immunoassays. We observed normalization of the thyroid stimulating hormone (TSH) and free T4 measurements when the patient withheld biotin for a week. As our case illustrates, early consideration of biotin interference minimizes unnecessary repeat laboratory studies. As trials in MS are progressing, we expect to see more patients on high-dose biotin treatment with spurious laboratory measurements. Therefore, we advise careful history taking and close communication with the laboratory when the clinical picture does not match with the laboratory results.