Partial Double-Blind, Placebo-Controlled Study to Assess the Effect of Anastrozole on the Endometrium in Healthy Volunteers

Inclusion Criteria: * Between the ages of 25 and 45 and pre-menopausal; * Non-lactating and not pregnant * able to follow the schedule of procedures * able to freely provide informed consent * have clinically acceptable physical examination and safety laboratory studies Exclusion Criteria: * current use of any form of systemic contraceptive * have self-reported irregular menstrual cycles * intercurrent illness(es) detected on the screening physical * unwilling or unable to use barrier methods of contraception * have evidence of endometrial polyps or myomata on TVU/SIS that would interfere with endometrial thickness measurement * detection of ovarian cyst(s) during adnexal examination on screening TVU/SIS measuring greater than 5 cm * have history of, or current cancer, on any form exclusive of basal cell carcinoma * BMI \>= 35 * history of alcohol or drug abuse in the past 5 years * unwilling or unable to undergo study procedures within the necessary time frames * history or current liver abnormalities as defined by ALT or AST \> 2X ULN * treated or untreated diabetes defined as fasting blood sugar \>= 126 mg/dL * untreated hypertension * impaired renal function by estimated creatinine clearance \< 80mL/min * have estradiol levels \< 20 pg/ml and FSH levels \> 40 mIU/mL or * have a history of adverse reaction any aromatase inhibitor