Kisspeptin Administration in the Adult

A. Healthy Subjects All healthy subjects will meet the following criteria: * normal puberty with respect to onset and pace, * no chronic diseases, * no difficulty with blood draws, * no prescription medications for at least 2 months with the exception of seasonal allergy medications and hormone replacement therapy, * no illicit drug use or excessive alcohol consumption (\< 10 drinks/week), * no history of a medication reaction requiring emergency medical care, * normal physical exam and laboratory studies within protocol reference ranges. Additional criteria based on subject population: 1. Healthy Men: * between 21 and 40 years old, * normal erectile and ejaculatory function, no history of reproductive disorders, * testicular volume \>15 ml. 2. Healthy women: * between 21 and 40 years old, * not breastfeeding or pregnant, * menstrual cycles between 25 and 35 days in duration, at least 11 periods/year, with no more than 5 days variability in cycle duration, * no evidence for androgen excess (hirsutism or acne), * at screening, negative hCG pregnancy test, * negative screening for Factor V Leiden for those who might receive estradiol treatment as a part of this study. 3. Healthy postmenopausal women: * between 50 and 60 years old, * no menstrual periods within the last year, * previous history of menstrual cycles between 25 and 35 days in duration, with no more than 5 days variability in cycle duration, * if applicable, able to unde…