The endometrial effects of SERMs.

The ideal selective oestrogen receptor modulator (SERM) would retain an oestrogen-like effect on the bones, the heart and cardiovascular apparatus, and the central nervous system, while acting as an anti-oestrogen on the breast and the genital tract. It seems, however, that such a compound is not available for clinical use yet. The uterine tissue, and particularly the endometrium, defines an area of special interest in the SERM action, since endometrial hyperplasia and cancer has been linked to agonistic oestrogen effects. Additionally, tamoxifen, the SERM which accumulates most of the clinical experience, has been associated with stimulatory effects on endometrium, including the development of cancer. In contrast, the more recent benzothiophenes, led by raloxifene, seem to operate as endometrial antagonists, thus providing an interesting alternative for clinical use. This review analyses the endometrial action of tamoxifen, including the information gathered from laboratory models, the observed endometrial effects in women using tamoxifen, and the epidemiological and molecular data which link the use of tamoxifen with endometrial cancer. A parallel examination of the raloxifene data presents the available experimental and clinical information, suggesting the endometrial neutrality of this compound.