Endocrine Abstracts

Background: In the last decade, the combination of the widespread use of streptavidin-biotin technology and biotin–containing supplements (BCS) in the daily clinical practice, have led to numerous reports of erroneous hormone immunoassay results. However, there are no studies assessing the clinical and biochemical significance of that phenomenon, when treating patients with hypothyroidism. Therefore, a prospective study was designed to investigate the potential alterations in the measurement of thyroid hormone concentrations and clinical consequences in patients with hypothyroidism using low -dose BCS containing less than 300μg/day.

Methods: 57 hypothyroid patients on thyroxine supplementation, as a result of hypothyroidism and concurrent use of BCS at a dose <300μg/day for 10 to 60 days were prospectively evaluated. Namely, TSH and free T4 (FT4) concentration measurements were performed, during BC supplementation and 10 days post BCS discontinuation and compared to 31 age-matched patients with hypothyroidism and normal thyroid hormones levels.

Results: A statistically significant increase in TSH and decline in FT4 concentrations was observed after BCS discontinuation. However, on clinical grounds, these modifications were minor and led to medication dose adjustment in only 2/57 patients (3.51%) in whom TSH was notably decreased after supplement discontinuation. Regarding the impact of biotin dose on thyroid hormone levels, no statistical significant correlation was detected between the biotin dose ingested in either TSH (r2= -0.09, P=0.53) or FT4 levels (r2 = 0.08, P=0.52). Significant increase in TSH levels was revealed only in the subgroup of patients that were taking BCS in doses > 100 μg daily

Conclusion: Our study suggests that changes in thyroid hormones profiling, due to supplements containing low dose biotin, are of minimal clinical relevance and in most cases don’t hide the need to adjust the thyroxine replacement dose in patients with hypothyroidism. Larger, well-designed trials are required to further evaluate this phenomenon.