The study will take place over the course of about 5 months. Each subject will take two different medications over two six-week periods. They will be randomized at the beginning of the study to either estradiol+medroxyprogesterone acetate or estradiol+drospirenone for the first period, and will receive the other medication the second six-weeks of the study. At the very beginning of the study and at the end of each six-week treatment period, subjects will come to the hospital various tests including non-invasive blood vessel imaging tests, blood draws to test the levels of certain hormones in the body, an oral glucose tolerance test, a test to monitor renal blood flow, and 24-hour blood pressure monitoring. Between treatment periods, there will be a four-week medication-free washout period.