Assessment of Sensitivity of the Hypothalamic GnRH Pulse Generator to Estradiol and Progesterone Inhibition

Inclusion Criteria: * Girls ages 8 to 14 * Tanner 1-3 pubertal stage * Pre-menarchal * Normal screening labs Exclusion Criteria: * Abnormal screening labs * Congenital adrenal hyperplasia * Hyperandrogenism (e.g., hirsutism, elevated free testosterone level) * Hemoglobin \<12 mg/dL or hematocrit \< 36% (Subjects will be offered the opportunity to take iron supplementation for 60 days if their hematocrit is slightly low (33-36%) (suggestive of iron deficiency anemia) and will then return for retesting of their hemoglobin/hematocrit.) * Weight \< 31 kg * History of peanut allergy, deep venous thrombosis, breast cancer, endometrial cancer, or cervical cancer * On hormonal medications (including oral contraceptive pills) or on medications known to affect the reproductive axis within 3 months of the study * Pregnant or breast feeding * Participation in a research study within the past 30 days that involved taking a study drug. * Participation in a research study that involved taking up to or greater than 473 ml's of blood within the past 60 days. * Cigarette smoking * History of surgery that required bedrest within the past 30 days * Family history of hypercoagulability or unexplained thromboembolic disease (not in setting of bedrest, surgery, or malignancy) * In order to ensure an adequate number of younger girls, no more than 4 enrolled subjects will be Tanner stage 3