Women with normal ovarian function ages 18 to 55 and postmenopausal women 60 years of age or older may be eligible for this study. Candidates will be screened with a medical history, physical examination, blood tests and vaginal ultrasound examination. For the ultrasound study, a probe that emits sound waves is inserted into the vagina, and the sound waves are converted to form images of the ovaries. The procedure is done with an empty bladder and takes about 10 minutes. After this screening visit (Visit 1), those enrolled in the study will return to the NIH Clinical Center for the following additional procedures: