Neuropeptides in Human Reproduction

Inclusion Criteria: * Ages 21-40 (healthy men and regularly cycling women) OR ages 18-75 (men and women with hypogonadotropic hypogonadism (HH)) * Normal blood pressure (systolic BP \<140 mm Hg, diastolic BP \<90 mm Hg) * White blood cell, platelets, prolactin, and thyroid stimulating hormone (TSH)within 90%-110% of laboratory reference range * Negative urine drug screen panel * Hemoglobin: 1. For healthy men and healthy regularly cycling women: normal 2. For men and women with HH: No less than 0.5 gm/dL below the lower limit of the reference range for normal women * Blood urea nitrogen (BUN), creatinine, liver function tests not elevated * For healthy subjects: Normal reproductive function and history * For healthy subjects: Body Mass Index (BMI) 18.5-30kg/m2 * For subjects with HH: All medical conditions stable and well controlled Exclusion Criteria: * History of medication reaction requiring emergency medical attention * Illicit drug use * Consumption of more than 10 alcoholic drinks per week * Difficulty with blood draws * Currently seeking fertility, breastfeeding, or pregnant * For healthy subjects: history of chronic disease and prescription medication use (with the exception of seasonal allergy medication) * For subjects with HH: prescription medications known to affect reproductive endocrine function except for those used to treat the subject's reproductive condition