Estrogen Use in Protection From Cognitive Decline

Inclusion Criteria: * Women between the ages of 45 and 65 * Currently on hormone replacement * One year or more post complete cessation of menses * Willing to sign the Human Subject Protection Consent form prior to enrollment in the study * Willing to be randomized to continue or discontinue estrogen therapy * Adequately visually and auditorially acute to allow neuropsychological testing * Beyond 8 years of educational achievement to allow adequate neuropsychological testing * Willing to undergo brain imaging * At risk for cognitive decline, as defined by one or more of the following: Personal or family history of mood disorder, Hypothyroidism, Diabetes, Family history of Alzheimer's, APOE-4 allele Exclusion Criteria: * Diagnosis of possible or probable Alzheimer's disease or dementia * Cerebrovascular disease or uncontrolled hypertension (systolic BP \>170 or diastolic BP \>100) * History of myocardial infarction within previous year or unstable heart disease * History of significant liver disease, pulmonary disease, or current cancer * Contraindication for MRI (metal in body, claustrophobia, etc.)