This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The overall goal of this protocol is to investigate the control of reproduction and to better understand the role of gonadotropin-releasing hormone (GnRH) in human male reproduction. In this study, men with GnRH deficiency (also known as Kallmann syndrome) are treated with pulsatile GnRH for 7 days and hormonal changes are measured. This provides information about an individual's response to GnRH and provides important information for our additional study looking into the genetic causes of this disease.