In addition to estrogen treatment for osteoporosis, naturally occurring phytoestrogens, such as quercetin,296 icariin,366,367 kaempferol,368,369 and genistein,370,371 have shown therapeutic effects in female patients with osteoporosis.372,373 Isoflavones, a kind of phytoestrogen with lower binding affinity than endogenous estrogens, can act as an ERβ selective ligand and an inhibitor of testosterone 5-α reductase to maintain the balance of estrogen/androgen to promote bone health.374. This evidence concerns the gene ESR2 and osteoporosis.