Bone Mass Accrual in Adolescent Athletes

Inclusion Criteria: * Female * 18-21 years of age * Hypothalamic amenorrhea * Greater than or equal to 15 years bone age * BMI between 10th-90th percentiles for age Exclusion Criteria: * Use of medications affecting bone metabolism including estrogen/ progesterone, anabolic steroids and glucocorticoids except local application of glucocorticoid creams (washout period of three months necessary prior to study enrollment if medically permissible to discontinue these) * Presence of anorexia nervosa or %IBW of \< 85% based on the 50th %ile of BMI for age * Spine BMD Z-score \< -3 * Conditions other than endurance training that may cause amenorrhea including PCOS (clinical or preceding laboratory evidence of hyperandrogenism with amenorrhea) * Conditions other than endurance training that may cause bone metabolism to be affected * Abnormal TSH, elevated FSH, hematocrit \< 30% * Pregnancy For girls with AA (to be randomized to estrogen and progesterone or no treatment) * History of migraines, hypertension, allergy to peanut oil, undiagnosed abnormal genital bleeding, known, suspected or history of breast or genital cancer or estrogen dependent neoplasia, known hypersensitivity to progesterone or estrogen or other product ingredients, liver dysfunction or disease * LFTs greater than 1.5 times the upper limit of normal * Family history or personal history of conditions that may increase risk of thromboembolism: 1. Family history of myocardial infarction or strokes occurring at less than 50 years 2. Family history of clotting disorders: normal coagulation profile will be necessary for enrollment * History of smoking \>10 cigarettes a day (history of smoking \>14 cigarettes a day is a contraindication for estrogen, but we will be more conservative in our exclusion criteria) * Personal history of blood clots