Hormonal Regulation of Puberty and Fertility

Background: \- The body produces gonadotropin-releasing hormone (GnRH) about every 2 hours. GnRH travels through the bloodstream to the pituitary gland, where it stimulates the gland to produce hormones called gonadotropins. These hormones stimulate the testicles or ovaries. The testicles produce testosterone and develop sperm. The ovaries produce estrogen and prepare for ovulation. Normal estrogen and testosterone levels are required for puberty. Some people, however, have either low levels or total lack of GnRH. This can cause problems with puberty and fertility. Researchers want to study people with low or no GnRH to better understand how it affects puberty and fertility. Objectives: \- To study disorders of GnRH production. Eligibility: * Adult men and women at least 18 years of age with low or no gonadotropin levels. * Adolescents between 14 and 18 years of age with low or no gonadotropin levels. Design: * Participants will be screened with a physical exam and medical history. Blood and urine samples will be collected. * Participants will have tests to look at their hormone levels. Blood samples may be collected after taking different drugs, including insulin and cortisone. A 24-hour urine sample will be collected. * Participants will have imaging studies to look at bone and brain development. They will also have ultrasounds of the kidneys, abdomen, and reproductive organs. * Tests of smell and hearing will be used to look for abnormalities in these senses.