Calorie Restriction, Environment, Fitness, Reproduction

Background: Functional hypothalamic amenorrhea (functional HA) is a condition where a woman s period stops for a temporary time. This is due to improper function of the hypothalamus. This is the part of the brain that directs the whole reproductive system. Researchers want to learn more about functional HA. They also want to learn how diet, exercise, and other factors may change women s menstrual cycles. Objective: To better understand functional HA. Eligibility: Healthy women ages 18-28 years old who: - Have regular periods - Exercise no more than 4 hours a week - Had their first period at age 11-14 Design: Participants will be prescreened over the phone. Participants will be screened with: - Blood and urine tests - Medical history - Physical exam. Participants will have 9 or 10 visits over about 3 menstrual cycles. These include: - Repeat of screening tests - Questionnaires - Exercise test - Resting energy expenditure test: Participants fast overnight before the test. They lie on their back under a canopy for a half hour. - Body composition test: This is done with a dual energy x-ray absorptiometry (DXA) scan. - Pelvic ultrasound - For two full-day visits, an IV is inserted into an arm vein. The IV takes a blood sample every 10 minutes for 8 hours. Participants will keep logs: - Menstrual cycle log - Diet log for three 4-day cycles Participants will receive test kits to complete at home: - Daily blood and urine sample - Ovulation Participants will take a daily iron supplement. They will wear a wristband that monitors activity 24 hours a day. Participants will stick to a special diet for two 5-day periods of time. They will complete two 4-day exercise programs. ...