We have seen discussions about the effect of biotin on thyroid tests (TSH, FT4 and FT3). This paper has the singular advantage of concentrating on the results for a single person in particular circumstances.
That means, we see the specific effects of the biotin on one assay but not on another. Very roughly, FT4 doubled and FT3 tripled on one assay (the one affected by biotin) but the other was essentially unchanged.
(TSH did not change and that was one reason to have been suspicious of the other results .)
That was the effect of 72 milligrams of biotin a day. Which is certainly a high dose but some previous reports have been when taking even more - such as 300.
Being a concrete example describes the issue in a way which is straightforward.
My view is that the first step is that any labs which use tests affected by biotin should ask doctors, nurses, phlebotomists to ask patients. The second to enhance further what we have done on this forum, spread the information. And third, to ensure that assays are changed to stop them being susceptible to this interference.
In the meantime, it is necessary to consider the possibility of biotin interference. Especially when odd results are reported.
Endocr J. 2023 Jun 17.
doi: 10.1507/endocrj.EJ23-0062. Online ahead of print.
Elevated free thyroxine and free triiodothyronine probably caused by high-dose biotin intake in a patient with Graves' disease: a case report
Kento Shimmaru 1 2 , Mitsuhiro Inami 1 , Aya Hamaoka 1 , Noriko Fujiwara 1 , Tomoaki Morioka 2 , Masanori Emoto 2 , Nozomu Kamei 1
PMID: 37331797 DOI: 10.1507/endocrj.EJ23-0062
Abstract
Biotin is a water-soluble vitamin that acts as a cofactor for carboxylase, and is often used as a component in several immunoassays. We present a case of a 46-year-old male with Graves' disease (GD) who revealed elevated free thyroxine (FT4) and free triiodothyronine (FT3) levels after high-dose biotin intake. Levels of these hormones had been within the reference range when he was on thiamazole 5 mg/day for 7 years; however, the levels increased from 1.04 to 2.20 ng/dL and from 3.05 to 9.84 pg/mL for FT4 and FT3, respectively, after he started taking biotin 72 mg/day. Despite these high levels, his symptoms and the other laboratory results, including the thyroid-stimulating hormone level, did not suggest GD relapse. His thyroid hormone data was decreased and returned within the reference range immediately after the laboratory assays for FT3 and FT4 had been coincidentally changed from those containing streptavidin-biotin complexes to biotin-free ones. Biotin interference, which is caused by high-dose biotin intake and immunoassays using some form of streptavidin-biotin complex, is sometimes clinically problematic, giving high or low results. To our knowledge, this is the first case report of a patient with GD on high-dose biotin receiving high thyroid hormone level results that were initially misunderstood as an aggravation of the disease; there are some reports of misdiagnosis of hyperthyroidism due to biotin administration. Unexpected fluctuations in thyroid function test results in patients with GD should be checked for biotin intake, immunoassays and the limiting concentration of biotin to avoid misdiagnosis of relapse.
Keywords: Biotin interference; Graves’ disease; Immunoassay; Streptavidin-biotin complex; Thyroid hormone.
Full paper freely accessible here:
Diarrhoea, high ft3 low ft4.
Pls help with tests interpretation for fT3 and fT4
Is there any point in testing for rT3, fT4,fT3?
The DI01 mutation causes a change in the FT3/FT4 ratio
