[Bone and hormones. Estrogens and antiestrogens: action on osteoporosis]

ESTROGEN INSUFFICIENCY: Estrogens play a cardinal role in bone tissue in women. Estrogen insufficiency leads to accelerated bone loss within 5 to 8 years after menopause. HORMONE SUBSTITUTION THERAPY: Substitution therapy prevents postmenopausic bone loss (lumbar vertebrae, hip, radius) and reduces the risk of osteoporotic fracture. Cohort studies have demonstrated that women given hormone substitution therapy for at least 7 years have a significantly higher bone density than untreated women. Although still controversial, it would appear that the risk of breast cancer increases with prolonged use of hormone substitution therapy. SERM: Observations in patients given tamoxifen, an antiestrogen used in the treatment of breast cancer, have led to the concept of selective estrogen receptor modulators (SERM), a new class of compounds with estrogen agonistic or antagonistic activity, depending on the tissue. Among these molecules, raloxifen has reached advanced clinical testing phases. Phase III trials have demonstrated that raloxifen can prevent bone loss and reduce the risk of vertebral fractures while reducing total cholesterol and LDL-cholesterol in menopaused women without stimulating the endometrium. SERMs are a promising alternative to hormone substitution therapy for the treatment of menopaused women.