This purpose of this study is to gain information about normal ovarian function that will be useful in developing a test for early detection of ovarian failure. The ovaries produce female hormones, such as estrogen, that are important in maintaining a woman's health. When the ovaries do not work properly, problems can develop. Unfortunately, there is no test that can detect ovarian failure early in its course. By the time premature ovarian failure is diagnosed in young women, two-thirds have already developed osteopenia (loss of some bone mass) and nearly one in ten have osteoporosis, a greater loss of bone mineral density that weakens bones and increases the risk of fractures.