An attempt to determine if pituitary responsiveness to GnRH (gonadotropin releasing hormone) is enhanced at low GnRH doses in healthy older men compared to young men. With aging, the amount of testosterone secreted by the testes diminishes. It is thought to play an important role in age associated disabilities such as loss of muscle mass, loss of muscle strength, decreased bone density, hip fracture, loss of sexual function, and diminished sense of well being. The issue is of enormous importance to the current veteran population, being overwhelmingly male, older, and with greater chance of falling due to muscle weakness. Breaks of osteoporotic bones can result in long-term nursing care. The first objective of this study is to test the hypothesis that age alters the sensitivity of the dose-responsive relationship between GnRH and LH (luteinizing hormone). The second objective is to test the hypothesis that the Leydig cells (clusters of cells that make up the endocrine tissue of the testes) of older men are less capable of secreting youthful quantities of testosterone when stimulated by doses of LH given to the subject at regular intervals. There will be 30 male subjects, of any race, for each of the parts of the randomized, controlled trial parts of the study. Ages will be between 20-40 and 60-80. All subjects will be entirely healthy men with no acute or chronic illnesses within four weeks before entering the study. Weight will be within 20% of ideal. The subjects will be recruited from the community through computerized search of elderly male veterans registered in two Veterans Affairs data banks at Richmond and Salem, Virginia, as well as advertisement in public venues. At the beginning of the study, subjects will receive an injection of the medication which will temporarily shut off the bodies natural production of stimulatory hormones. Three weeks later, there will be a 36 hour admission to the General Clinical Research Center. Injections will be given every two hours and blood will be drawn every ten minutes to measure the production of testosterone.
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