Category: Thyroid

Monitor: 4

4 - BIOTIN INTERFERANCE WITH THYROID FUNCTION TESTING

Thursday, Apr 25
1:00 PM – 1:30 PM

Objective :

Biotin, also known as vitamin B7, is an over-the-counter (OTC), water-soluble B-complex vitamin. It is a co-factor of enzymes known as carboxylases. These biotin-containing enzymes play important roles in glucose and fatty acid metabolism. Some studies have shown that biotin is beneficial for skin, hair and nail growth; other studies have shown that biotin can be used to treat progressive multiple sclerosis. Biotin is a dietary supplement that is readily available OTC without prescription. It is sold as a stand-alone supplement under a variety of descriptions such as B complex vitamins as well as in multivitamin supplements. A dose of OTC biotin can be up to 10 mg/capsule. It has been reported that such high doses of biotin can interfer with the streptavidin/biotin-basedimmunoassays resulting in abnormal thyroid function test results. 


Methods : n/a


Results : n/a


Discussion :

A 50-year-old female with a history of post ablative hypothyroidism presented for routine follow up; she reported feeling well. She was taking a stable dose of levothyroxine 100mcg daily for treatment of post-ablative hypothyroidism with no recent changes in estrogen status. On routine lab testing, her TSH was found to be mildly suppressed at 0.310 mcu/mL (0.35 to 5.0 mcu/mL) with a significantly elevated free T4 at 4.7 ng/dL (0.6 to 1.6 ng/dL). Given labs that were discordant to the clinical picture, a careful review of supplements was undertaken with detection of the patient’s addition of biotin 10,000mcg daily to her daily regimen. The patient was asked to hold biotin with repeat labs ten days later revealing a normal TSH (0.350 mcu/mL) with normal free T4 (1.2 ng/dL).    

Biotin has been reported as an interfering assay on certain platforms; up to 60% of the most popular thyroid immunoassays are biotin based. In TSH sandwich assays, excess biotin displaces biotinylated antibody-antigen complexes resulting in falsely low TSH levels. In contrast, in competitive assays of free T4, excess biotin causes an overestimation of the hormone – as seen in our patient. Biotin interference in immunoassays is not expected with normal dietary intake of biotin; for those patients taking biotin supplementation, a biotin washout period of three or more days should be implemented prior to obtaining thyroid labs to avoid biotin interference. 







Conclusion :

Given the common use of OTC biotin, frequent non-reporting of supplement use, and high frequency of testing for thyroid dysfunction, the prevalence of biotin interference has the potential to be wide scale. By detecting that biotin usage was the etiology of abnormal thyroid function testing in this patient, appropriately, no alteration in thyroid replacement dosing was undertaken.

Leigh M. Eck

Associate Professor of Medicine
University of Kansas
Fairway, Kansas

Leigh M. Eck M.D. is an Associate Professor of Medicine at the University of Kansas Medical Center; Dr. Eck has been a member of the Department of Internal Medicine since 2008. Working alongside a fantastic medical education team, Dr. Eck serves as the Program Director for the Internal Medicine Residency Program; a role that she has held since July 2014. Dr. Eck and her team have the opportunity to teach, advise, mentor and coach 94 internal medicine resident physicians. Dr. Eck’s scholarly work is focused on assessing interventions to improve the well-being and training experience of the Internal Medicine resident physicians at the University of Kansas; current efforts of the Internal Medicine Residency Program medical education team include implementation of experiential learning experiences in quality and patient safety initiatives, implementation of simulation activities to improve competency in high stress clinical learning environments, development and implementation of a point of care ultrasound elective curriculum, and introduction of emotional intelligence coaching to residents in order to develop resilient physician leaders. On a national level, Dr. Eck has been involved in work with the American College of Physicians including a four-year term on the ACP Internal Medicine In-Training Examination Question Writing Committee as well as more recent authorship contributions to the endocrinology section of MKSAP 18 – a resource used by Internal Medicine residents across the US to prep for their certifying examination.

Lei Pei

Resident Physician
University of Kansas

Dr. Pei is a PGY3 resident physician at the University of Kansas; following completion of training in June 2019, Dr. Lei will work as a hospitalist physician at the University of Kansas. Prior to initiation of her clinical training, Dr. Lei completed her PhD with her research focused in the Division of Nephrology at the University of Kansas.

Leigh M. Eck

Associate Professor of Medicine
University of Kansas
Fairway, Kansas

Leigh M. Eck M.D. is an Associate Professor of Medicine at the University of Kansas Medical Center; Dr. Eck has been a member of the Department of Internal Medicine since 2008. Working alongside a fantastic medical education team, Dr. Eck serves as the Program Director for the Internal Medicine Residency Program; a role that she has held since July 2014. Dr. Eck and her team have the opportunity to teach, advise, mentor and coach 94 internal medicine resident physicians. Dr. Eck’s scholarly work is focused on assessing interventions to improve the well-being and training experience of the Internal Medicine resident physicians at the University of Kansas; current efforts of the Internal Medicine Residency Program medical education team include implementation of experiential learning experiences in quality and patient safety initiatives, implementation of simulation activities to improve competency in high stress clinical learning environments, development and implementation of a point of care ultrasound elective curriculum, and introduction of emotional intelligence coaching to residents in order to develop resilient physician leaders. On a national level, Dr. Eck has been involved in work with the American College of Physicians including a four-year term on the ACP Internal Medicine In-Training Examination Question Writing Committee as well as more recent authorship contributions to the endocrinology section of MKSAP 18 – a resource used by Internal Medicine residents across the US to prep for their certifying examination.