Menstrual Cycle Study in Adolescent Girls

* Part 1 - Pre-menarche monitoring ("holding pattern"): Inclusion Criteria: * Age 8-14.5 years old * Healthy weight, defined as having a body weight \>85% of expected (EBW) and a body mass index (BMI) \<99th percentile * Some breast development * Pre-menarche Exclusion Criteria: * Taking or planning to take medications that affect reproductive hormones in the next 2 to 3 years (e.g. birth control pills, biotin supplements). * Planning to move more than 60 miles from the CRU within the next 2 to 3 years * Chronic medical condition, including but not limited to diabetes mellitus, congenital adrenal hyperplasia, cystic fibrosis, sickle cell disease, inflammatory bowel disease, juvenile rheumatoid arthritis, and lupus. * First-degree relative with polycystic ovarian syndrome, premature ovarian insufficiency, hypogonadotropic hypogonadism, or other pubertal development disorder * Excessive exercise (defined as running \>20 miles per week or its equivalent) * Pregnancy Part 2 - Post-menarche cycle tracking: Inclusion Criteria: * Age at menarche 10-14.5 years old * Healthy weight, defined as having a body weight \>85% of expected (EBW) and a body mass index (BMI) \<99th percentile * Approximately \< 6 months post-menarchal (will typically have completed 4 or fewer menstrual cycles) * Biochemical criteria: normal thyroid hormone, prolactin, and testosterone levels Exclusion Criteria: * Taking or planning to take medications that affect reproductive hormones in the next 2 to 3 years (e.g. birth control pills, biotin supplements). * Planning to move more than 60 miles from the CRU within the next 2 to 3 years * Chronic medical condition, including but not limited to diabetes mellitus, congenital adrenal hyperplasia, cystic fibrosis, sickle cell disease, inflammatory bowel disease, juvenile rheumatoid arthritis, and lupus. * First-degree relative with polycystic ovarian syndrome, premature ovarian insufficiency, hypogonadotropic hypogonadism, or other pubertal development disorder * Excessive exercise (defined as running \>20 miles per week or its equivalent) * Anemia (defined as hemoglobin \<12.0 g/dl) --Participants with hemoglobin between 11.5 g/dl and 12.0 g/dl may still participate by providing dried blood spots, or no more than 18 ml of blood during any given interval. * Pregnancy Part 3 - Intensive monitoring of ovarian follicle growth Inclusion Criteria: * Age at menarche 10-14.5 years old * Healthy weight, defined as having a body weight \>85% of expected (EBW) and a body mass index (BMI) \<99th percentile * Within 1 year of menarche * Biochemical criteria: normal thyroid hormone, prolactin, and testosterone levels Exclusion Criteria: * Taking or planning to take medications that affect reproductive hormones in the next 1-2 years (e.g. birth control pills, biotin supplements). * Planning to move more than 60 miles from the CRU within the next year * Chronic medical condition, including but not limited to diabetes mellitus, congenital adrenal hyperplasia, cystic fibrosis, sickle cell disease, inflammatory bowel disease, juvenile rheumatoid arthritis, and lupus. * First-degree relative with polycystic ovarian syndrome, premature ovarian insufficiency, hypogonadotropic hypogonadism, or other pubertal development disorder * Excessive exercise (defined as running \>20 miles per week or its equivalent) * Anemia (defined as hemoglobin \<12.0 g/dl) --Participants with hemoglobin between 11.5 g/dl and 12.0 g/dl may still participate by providing dried blood spots, or no more than 18 ml of blood during any given interval. * Pregnancy Part 4 - Late Post-menarche cycle tracking: Inclusion Criteria: * Age 11-17.5 years old * Approximately 2-5 years post-menarchal * Biochemical criteria: normal thyroid hormone and prolactin Exclusion Criteria: * Taking or planning to take medications that affect reproductive hormones in the next 2 to 3 years (e.g. birth control pills, biotin supplements). * Planning to move more than 60 miles from the CRU within the next 6 months * Chronic medical condition, including but not limited to diabetes mellitus, congenital adrenal hyperplasia, cystic fibrosis, sickle cell disease, inflammatory bowel disease, juvenile rheumatoid arthritis, and lupus. * Anemia (defined as hemoglobin \<12.0 g/dl) --Participants with hemoglobin between 11.5 g/dl and 12.0 g/dl may still participate by providing dried blood spots, or no more than 18 ml of blood during any given interval. * Pregnancy Adolescent girls, at-risk daughters, or sisters of women with PCOS The girls with mothers or sisters with PCOS group will complete the Screening Visit and Parts 1-3. The same inclusion and exclusion criteria apply for Parts 1, 2, and 3 as stated above except that these individuals must have a first-degree relative with PCOS and they can have high androgen levels, excess body hair, and severe acne at screening. Women with known PCOS (activities for 8 weeks only) Inclusion Criteria: * Age \>=18-34 years old * PCOS diagnosis * at least 3-years post-menarchal with irregular menstrual cycles * Biochemical (blood) or clinical signs of high androgen levels Exclusion Criteria: * Cannot be taking any medications that affect reproductive or metabolic hormones (e.g. birth control pill, biotin supplements, spironolactone, metformin). * Chronic medical condition, including but not limited to diabetes mellitus, congenital adrenal hyperplasia, cystic fibrosis, sickle cell disease, inflammatory bowel disease, juvenile rheumatoid arthritis, and lupus. * Pregnancy Healthy control women (Activities x 2 menstrual cycles) Inclusion Criteria: * Age \>=18-34 years old * at least 3-years post-menarchal with regular menstrual cycles every 21-35 days Exclusion Criteria: * Cannot be taking any medications that affect reproductive or metabolic hormones (e.g. birth control pill, biotin supplements, spironolactone, metformin). * Chronic medical condition, including but not limited to diabetes mellitus, congenital adrenal hyperplasia, cystic fibrosis, sickle cell disease, inflammatory bowel disease, juvenile rheumatoid arthritis, and lupus. * PCOS diagnosis or first-degree relative with disorder * Pregnancy Mothers of pediatric participants (Activities for 8 weeks / 2 menstrual cycles) Inclusion Criteria: * Age \>=18-65 years old * Biological mother of A Girl's First Period participant Exclusion Criteria: * Chronic medical condition, including but not limited to diabetes mellitus, congenital adrenal hyperplasia, cystic fibrosis, sickle cell disease, inflammatory bowel disease, juvenile rheumatoid arthritis, and lupus. * Pregnancy