Using ovariectomized rats as a model for the menopause, we found that TG-decoction (1) elevated E2 in serum but not in the hypothalamus; (2) had antioxidative activity and tissue-protective function; and (3) upregulated expression of ERα and β in the hypothalamus.
The mild estrogen-like effects of TG-decoction are reasonable because several of its constituents are known to contain flavonoid aglycones (kaempferol, apigenin, quercetin, luteolin and breviflavone B), which have estrogen-like activity . The complete composition of this decoction is being elucidated in ongoing studies that may identify additional compounds with estrogen-like effects.
Results of previous studies regarding expression of ERs in ovariectomized rats and upon E2 treatment are controversial [29–32]. In our study, expression of ERs decreased in the hypothalamus of ovariectomized rats and increased upon treatment with TG-decoction. Similar results have been recently reported by Wu et al.  who have found that total flavonoids of Epimedium sagittatum reversed the markedly reduced ERα expression in the hypothalamus of ovariectomized rats. The impact of ovariectomy and estrogen treatment on the expression of ERα and β varies in different parts of the rat brain [34, 35]. Also, within the hypothalamus, ER expression may differ in various subregions during aging [20, 21]. Further studies are necessary to find out how the expression of ERs in various subregions of the hypothalamus is influenced by the TG-decoction.
TG-decoction exhibited antiaging and tissue-protective activities in this study. Some of these activities may be direct and not mediated by ERs. In fact, antioxidative and cellular protective activities have been reported previously for several constituents of TG-decoction including yín yáng huò (Herba epimedium) , bā jí tiān (Radix morindae officinalis) , shēngdì huáng(Radix rehmanniae)  and zhīmǔ (Rhizoma anemarrhenae)[39, 40]. Phytoestrogens, for example, genistein in soya, are also known to be antioxidative by suppressing formation of reactive oxygen species and preventing release of cytochrome c from mitochondria . Furthermore, neuroprotective effects have been reported for quercetin (a phytoestrogen) and 17β-estradiol, which are probably not mediated via ERs but are rather based on their antioxidant and free radical scavenging properties .
Estrogenic activity of some compounds of the TG-decoction and their derivatives and/or metabolites may also indirectly contribute to the observed antiaging activities. Upon binding ERs, estrogen upregulates expression of antioxidant enzymes via intracellular signaling pathways [41, 43]. Recently, ERs have been identified in mitochondria  and E2 treatment has been reported to increase the level of ERα in mitochondria and to modulate mitochondrial function, resulting in greater energy-producing capacity and decreased reactive oxygen species production .
With regard to TCM, TG-decoction regulates balances of yin-yang, exterior-interior, cold-hot and deficiency-excess, and thus ameliorates menopausal symptoms and overall body health, and contributes to general well being. To shed light on the mechanism of efficacy of this herb mixture in treating menopausal syndrome and in promoting global health, further studies are in progress, including those aiming to define the precise composition and identify targets of this herb mixture.