Hypogonadal states in the male.

Male hypogonadism may be viewed either as a structural or functional abnormality of the testes; in most instances these usually go together. Dysfunction of the testes may involve the sperm-producing compartment alone (seminiferous tubules) or there may be a concomitant disorder of the testosterone-producing compartment (Leydig cells). Abnormalities of Leydig cell function are almost invariably associated with germ cell dysfunction, although the converse is not necessarily true. If male factor infertility is included, then hypogonadism in the male becomes an extremely common phenomenon affecting between 5% and 10% of the adult male population. If we understand the developmental steps in the formation of the male phenotype and the subsequent hormonal control of male reproductive physiology in the adult, the pathophysiology of various hypogonadal states becomes easier to elucidate and rational therapy can be planned.