Hormone Modulation

It appears unlikely that black cohosh exerts oestrogenic activity. Although oestrogenic activity has been detected in some tests (Düker et al 1991, Kruse et al 1999, Liu et al 2001) it has not been observed in others (Beck et al 2003, Einer-Jensen et al 1996, Zierau et al 2002). Additionally, the herb has demonstrated anti-oestrogenic activity in one test (Zierau et al 2002) and in 2003, black cohosh was investigated in a variety © 2007 Elsevier Australia

of different assays and did not demonstrate oestrogenic activity in any assay system (Lupu etal 2003).

More recently, results from a study using black cohosh extract BNO 1055 in ovariectomised rats found it has selective oestrogen receptor modulator activity with no action in the uterus, but beneficial effects in the hypothalamopituitary unit and in the bone (Seidlova et al 2003). This has been confirmed in a double-blind, randomised, multicentre study using the same black cohosh extract (Wuttke et al 2003). In that study, the herbal extract was equipotent with conjugated oestrogens in reducing menopausal symptoms, had beneficial effects on bone metabolism and significantly increased vaginal superficial cells; however, it did not exert uterotropic activity.

Overall it is generally agreed that black cohosh reduces LH secretion. This has been confirmed in a human study and is believed to be the result of at least three different active constituents acting synergistically (Duker et al 1991).

Clinical note - Selective oestrogen receptor modulators

These are compounds that, in contrast to pure oestrogen agonists or antagonists, have a mixed and selective pattern of oestrogen agonist-antagonist activity, which largely depends on the tissue targeted. The therapeutic aim of using these substances is to produce oestrogenic actions in those tissues in which it would be beneficial (e.g. bone, brain, liver) and have either no activity or antagonistic activity in tissues, such as breast and endometrium, where oestrogenic actions (cellular proliferation) might be deleterious. They are a relatively new class of pharmacologically active agents and are being used by women who cannot tolerate pharmaceutical HRT or are unwilling to use it. The most actively studied are tamoxifen and raloxifen (Hernandez & Pluchino 2003).

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