Background: Natural compounds with potential antioxidant properties have been used in the form of
food supplements or extracts with the intent to prevent or treat various diseases. Many of these compounds can
activate the cytoprotective Nrf2 pathway. Besides, some of them are known to impact the thyroid gland, often
with potential side-effects, but in other instances, with potential utility in the treatment of thyroid disorders.
Objective: In view of recent data regarding the multiple roles of Nrf2 in the thyroid, this review summarizes the
current bibliography on natural compounds that can have an effect on thyroid gland physiology and pathophysiology,
and it discusses the potential implication of the Nrf2 system in the respective mechanisms.
Methods & Results: Literature searches for articles from 1950 to 2018 were performed in PubMed and Google
Scholar using relevant keywords about phytochemicals, Nrf2 and thyroid. Natural substances were categorized
into phenolic compounds, sulfur-containing compounds, quinones, terpenoids, or under the general category of
plant extracts. For individual compounds in each category, respective data were summarized, as derived from in
vitro (cell lines), preclinical (animal models) and clinical studies. The main emerging themes were as follows:
phenolic compounds often showed potential to affect the production of thyroid hormones; sulfur-containing compounds
impacted the pathogenesis of goiter and the proliferation of thyroid cancer cells; while quinones and terpenoids
modified Nrf2 signaling in thyroid cell lines.
Conclusion: Natural compounds that modify the activity of the Nrf2 pathway should be evaluated carefully, not
only for their potential to be used as therapeutic agents for thyroid disorders, but also for their thyroidal safety
when used for the prevention and treatment of non-thyroidal diseases.