Women undergoing surgical menopause often experience marked menopausal side effects but are reluctant to use estrogen or other female hormones to ease the transition to menopause because of worries that the hormones may increase breast cancer risks. This study will evaluate tibolone in women experiencing surgical menopause to assess its effects on bone health, menopause symptoms and breast density.

Women interested in participating in this study will be allowed to use hormones to manage symptoms for up to 3 months before beginning the study. Those choosing not to take hormones may enroll in the study immediately.

All women will have a baseline mammogram, breast examination, and bone study density performed, along with blood and urine analysis for measurement of bone markers. They will also be asked to take a questionnaire.

Patients will take either tibolone or placebo once daily for 1 year. Neither the patient or the physician will be aware of which treatment a woman is taking during the study.

Patients will return at 6 and 12 months to have a physical examination, blood work, urine collection and bone studies. At one year, a repeat mammogram will be performed. There are also some questionnaires asking about menopause symptoms that will be performed at intervals during the study.

It is also recommended that patients take calcium and vitamin D throughout the study.

Inclusion Criteria:

• Good overall health
• Premenopausal at the time of enrollment if before their oophorectomy
• Will undergo or have undergone an oophorectomy
• Negative breast examination and negative breast imaging studies

Exclusion Criteria:

• History of breast cancer, ductal carcinoma in situ (DCIS) or other cancer except for carcinoma in situ of the cervix or basal cell carcinoma of the skin
• History of ovarian cancer, breast cancer (or DCIS) or other malignancy
• Low bone mass compared with age-adjusted controls
• Current or recent exposure (within 3 months) to medications that alter bone metabolism
• Estrogens, progesterones, androgens, tamoxifen or raloxifene within 3 months of randomization
• History of significant medical problems potentially related to estrogens
• History of Paget's disease of bone, ankylosing spondylitis, rheumatoid arthritis or other metabolic bone disease, vitamin D deficiency, hyperparathyroidism, or newly diagnosed hyperthyroidism
• Body mass index (BMI) > 32
• High-density lipoprotein (HDL) cholesterol < 40 mg/dl
• Women whose uterus was retained and who have a history of uterine abnormalities