Effects of phytochemicals on thyroid function and their possible role in thyroid disease.

About 1 of 10 women, particularly those older than 60 years of age, shows some degree of thyroid hormone deficiency. Thyroid diseases are generally characterized by perturbations of thyroid signaling homeostasis. The most common examples of thyroid diseases include hypothyroidism, hyperthyroidism, and several types of thyroid cancers. Phytochemicals have been shown to have either beneficial or detrimental effects on thyroid function. Some flavonoids have been reported to affect the expression and the activity of several thyroid-related enzymes and proteins, and for this reason some concerns have been raised about the possible thyroid-disruptive properties of foods enriched in these substances. On the other hand, the beneficial effects of some plant-derived compounds, such as myricetin, quercetin, apigenin, rutin, genistein, and curcumin, and their possible role as adjuvants for the treatment of thyroid cancers have been described. Here, the role of phytochemicals in thyroid signaling modulation and their possible beneficial or detrimental effects on thyroid disease risk are discussed.