Estrogen-like actions

Tamoxifen is discussed in Chap. 61, Breast Cancer raloxifene is discussed in Chap. 3, Osteoporosis. Raloxifene decreases bone loss in recently menopausal women without affecting the endometrium and has estrogen-like actions on lipid metabolism. It may exacerbate vasomotor symptoms, and it increases the risk of venous thromboembolism and stroke. 

It is of interest that studies with estrogens have shown that the inhibition of bone turnover found in short-term studies translates into increased BMD and decreased fracture rate in long-term studies (Ettinger et al, 1985 Field et al., 1993 Lufkin et al., 1992 Weiss et al., 1980). The estrogen-like action of SERMs in the bone should thus lead to a decrease in bone fractures as confirmed recently in the MORE trial (Cummings et al, 1999). 

Structural-Based Mechanisms of SERM Estrogen-Like Action... 

Phytoestrogens are plant-derived molecules with estrogen-like action. There are numerous reports on the potential beneficial role of nutritional phytoestrogens in human health (cancer chemoprevention, relief of postmenopausal symptoms, osteoporosis amelioration). Herbal extracts... 

Organochlorine pesticides are nerve poisons in both insects and mammals. Action mechanisms are complex and not yet fully understood. They have been shown to have estrogen-like effects (ref. 84a), to inhibit testicular growth and secondary sex characteristics in cockerels and mice (DDT), to induce persistent estrus in rats, and to affect fertility, gestation, lactation and survival times. 

Even in large doses silymarin is devoid of toxic effects and in particular has no harmful action an the embryo. In isolated cases, a mild laxative effect has been observed. Also, in a recent smdy, dietary silymarin administration enhanced mammary carcinogenesis in rats and mice possibly due to an estrogen-like activity. ... 

In recent years, new evidence has focused attention on the role of RNA in the regulatory action of estrogen. The biological activity of RNA extracted from estrogen-stimulated rat uteri has been studied and the results reveal that several estrogen-like phenomena can be induced by the material. In this work mixed uterine RNA has been extracted by methods that do not preferentially separate species of RNA so that it is not possible to associate the reported activities with a particular nucleic acid component (Segal et ah, 1965a). These proce-... 

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