Impact of Aromatase Inhibitor Therapy on Glucose Homeostasis and Diabetes Risk

Inclusion Criteria: * Post-menopausal women with hormone receptor positive breast cancer, ductal carcinoma in situ (DCIS), or with other high risk breast conditions. Post-menopause will be defined as women who experience 12 months of amenorrhea or have undergone bilateral salpingo-oophorectomy. * 25 women who are planning to start or are within 6 months of starting treatment with aromatase inhibitors, after consultation in breast clinic and cancer center. * 25 women who will be starting Tamoxifen (comparative group) * 25 healthy post menopausal women will also be recruited. Exclusion Criteria: * Established diagnosis of diabetes * Therapy with medications that could affect glucose metabolism * Screening fasting glucose ≥ 126 mg/dl, and/or HbA1c ≥ 6.5% * History of upper GI surgery that alters gastric emptying or causing malabsorption e.g., bariatric surgery, fundoplication