The Potential Dangers of Supplements and Herbal Products Marketed for Improved Thyroid Function

Victor Bernet; Ana-Maria Chindris


Expert Rev Endocrinol Metab. 2012;7(3):247-249. 

In This Article

Thyroid Hormones in Nutritional Supplements

Numerous natural products marketed today claim that they either contain thyroid extract or substances that have a positive effect on thyroid function or thyroid hormone metabolism, which are also purportedly both safe and beneficial for general health. Researchers have focused on verifying such statements by both analyzing the content of these products and studying their effects on human volunteers.

Csako et al. carried out an in vitro analysis measuring T4 and T3 levels in three generally available natural hormone preparations, and detected apparent T3 content by high-performance liquid chromatography in two out of three of these products.[9] Administration of twice the recommended dose to human volunteers did not lead to clinical consequences; however, the authors recommended against the use of "scientifically unsound and relatively expensive OTC thyroid preparations," with unproven therapeutic efficacy.

Recently, Kang et al. analyzed the T3 and T4 content in ten OTC products on the market, and found detectable levels of T3 in nine out of ten and T4 in five out of ten samples.[10] Some of these preparations, even taken at the recommended doses, would deliver T3 and/or T4 doses equal to or greater than what may be used on a prescribed basis under the supervision of a health provider.


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