Recently, I came across a case with no signs or symptoms of hyperthyroidism, yet during a routine checkup the reports showed low TSH with high T3 and T4 levels.
What made it more confusing was that the same pattern appeared in three consecutive test reports. We were all wondering how that was possible.
Then suddenly, our sir suggested: “Ask about any supplements she had taken before the tests… and repeat the thyroid profile after stopping them for 2–3 days.”
And guess what?
The repeat reports came back completely normal.
The real culprit behind those abnormal thyroid reports was — Biotin.
Biotin (Vitamin B7), a trendy supplement commonly taken for hair and nail growth, can significantly interfere with thyroid function tests. It may cause:
Falsely high T3 and T4 levels
Falsely low TSH levels
Even though the person’s actual thyroid function remains normal, the reports may mimic hyperthyroidism.
Why does this happen?
Many laboratory immunoassays use biotin–streptavidin technology to measure hormone levels. Excess biotin circulating in the blood interferes with this method and produces misleading results.
That’s why supplement history is just as important as symptom history before ordering investigations.
So before interpreting any abnormal thyroid profile… always ask: “What supplements are you taking?”
Do you know about other supplements that can interfere with laboratory test results like this?
MBH/PS
