Category: Thyroid

Monitor: 33

33 - When Thyroid Labs Do Not Add Up, Ask The Patient About Biotin!

Saturday, Apr 27
10:00 AM – 10:30 AM

Objective :

Supraphysiologic Biotin is used to treat diseases such as multiple sclerosis as well as certain genetic diseases in children. Biotin is heavily marketed as a beauty product (hair-nail-skin health). We present a case where over-the-counter (OTC) biotin consumption interfered with thyroid function studies (TFTs) which prolonged time to definitive diagnosis.  


Methods :

Case presentation

Results : A 58 year old female was seen for hypothyroidism diagosed 4 years ago with difficulty regulating her levothyroxine dosing. Free T4 level was elevated up to 2.5 ng/dl (0.6-1.37). However, she did not experience any symptoms of hyperthyroidism and physical exam was normal. Further history revealed consumption of biotin 10,000 mcg twice daily when the TFTs were done. Her TSH remained low. Free T4 and TSH levels were normal after discontinuation of biotin.

Discussion :

Certain TSH immunoassays uitilize a mixture of a biotinylated monoclonal TSH antibody and a ruthenium-labeled monoclonal TSH antibody. Ruthenium allows for the chemiluminescence detection. The signal produced will be directly proportional to the TSH level present. Excess biotin in the serum will result in reduced binding of the immune complexes which will lead to decreased chemiluminescence resulting in a falsely low TSH level.

Free T4 is most often measured by competitive immunoassays that utilize a T4-specific antibody labeled with a ruthenium complex. Excess free biotin displaces the complex from the solid phase, producing false elevations.

This patient required multiple repeat TFTs and endocrine specialty visits adding cost and inconvenience to both the patient and the medical system. Most clinicians may not be aware of their laboratory’s particular assay or this potential interference by biotin.

Conclusion :

We strongly advise asking your patients about any use of OTC biotin products, as they are often not listed in the medication record and can interfere with TFTs and other analytes subject to similar immunoassays. This will prevent unnecessary cost, and most importantly, prevent the anxiety and negative consequences of a wrong diagnosis.


Vengamamba Polu

Michigan State University
Lansing, Michigan

I am doing fellowship at Michigan State University

Saleh Aldasouqi

Professor of Medicine and Chief of Endocrinology
Michigan State Universtiy

Saleh Aldasouqi is a professor of medicine and chief of endocrinology at Michigan State University. His research areas include diabetes and thyroid.

Naveen Kakumanu

Assistant Professor of Medicine
MSU Endocrinology

Dr. Kakumanu joined the Department of Medicine at MSU on October, 2013. He graduated from Saint George’s University, School of Medicine in Grenada. He completed his residency in Internal Medicine at the Detroit Medical Center, Wayne State University and was Chief Medical Resident, ambulatory clinic preceptor at Harper/Hutzel University Hospital, Detroit Medical Center. He completed a Geriatric Fellowship at Wayne State University and received the Lavoisier Cardozo Award for Excellence in Geriatric Medicine. Endocrinology fellowship was completed at Henry Ford Hospital in 2013. He is board certified in Internal Medicine, Geriatric Medicine and Endocrinology. Has presented multiple posters and abstracts at the Endocrine Society, American Association of Clinical Endocrinologists and American Society for Bone and Mineral Research. His specialty in Endocrinology is diverse with interest in thyroid disorders, diabetes and bone metabolism.

Parvathy R. Sankar

Medical student
Michigan State University College of Osteopathic Medicine
East Lansing, Michigan

I am a third year medical student from Michigan State University College of Osteopathic Medicine completing my clerkship at Sparrow Hospital. I am very interested in pursuing Endocrinology in the future.

Ghaydaa H. Adawi

Endocrinology Fellow
MSU Endocrinology
Holt, Michigan

Endocrinology fellow at MSU Endocrinology