Genistein improves thyroid function in Hashimoto's thyroiditis patients through regulating Th1 cytokines.

Hashimoto thyroiditis (HT) is a common autoimmune disease. Genistein is an isoflavone with immunomodulatory functions in various diseases. In this double-blind, randomized, placebo-controlled clinical study, we investigated the effects of genistein on patients with HT. A total of 218 patients were recruited. Genistein treated patients had a significant increased T4, fT4 levels, as well as reduction in serum TSH, TPOAb and TgAb levels, compared with those receiving placebo. Furthermore, Th1 related cytokine IFN-γ and IL-2 changes after genistein treatment suggest the immune modulating effect of genistein is mediated through regulating the function of Th1 cells. Overall, the genistein administration was effective and well tolerated in HT patients. These results demonstrate an immunological effect of genistein on HT patients. Further studies are warranted to determine the longer-term effects and possible chemopreventive effects on thyroid cancer in HT patients.