DIETARY SUPPLEMENTS THAT CONTAIN BIOTIN DO NOT INFLUENCE FLUORESCENCE THYROID-STIMULATING HORMONE VALUES WHEN SCREENING FOR CONGENITAL HYPOTHYROIDISM IN NEWBORNS

Background
Biotin levels may interfere with immunological tests that use biotin-streptavidin complexes. Although the recommended daily intake (RDI) of biotin is 30 µg, some dietary supplements that are available without prescription contain double or even tenfold the RDI.

Material and methods
To asses if biotin levels influence thyroid-stimulating hormone (TSH) serum concentrations using two different methods (chemiluminescent assay [CLIA] and fluorescent immunoassay [FEIA]), 110 samples from newborns and 64 samples from pregnant women in the first trimester were collected. Participants completed a questionnaire regarding dietary supplement use. Biotin levels were determined using the ELISA technique.

Results
Biotin levels for newborns were 0.004-0.170 ng/ml and for pregnant women were 0.070-0.155 ng/ml (22 women were taking supplements containing from 30 µg to 35 mg of biotin). Biotin levels were below the value of 400 ng/ml stated by the manufacturer of the CLIA method to influence TSH levels. The FEIA manufacturer does not state the influence of biotin levels in the insert. Correlation tests results between TSH value and biotin were r=-0.1 for CLIA method and r=0.04 for FEIA method.

Conclusions
According to our results, TSH values are not influenced by biotin levels even if the RDI was exceeded.