postmenopausal status defined as history of at least 12 months without spontaneous menstrual bleeding or a documented hysterectomy and bilateral salpingo oophorectomy

breast density greater than 25%

no hormone replacement therapy for at least six months prior to entry into this study

non-smokers.

history of stroke, pulmonary embolism or deep vein thrombosis

history of atherosclerotic heart disease

presence of any known hypercoagulable state either congenital (e.g., protein s deficiency) or acquired (e.g., corticosteroid treatment)

diabetes mellitus

uncontrolled hypertension (bp ≥140/90)

presence of a psychiatric condition that would interfere with adherence to the protocol.