Late-onset hypogonadism (LOH) is a situation where a middle-aged or older man has low serum testosterone in conjunction with diffuse symptoms resembling those of genuine male hypogonadism. Testosterone replacement therapy has become a popular choice for the treatment of LOH. Aging is a process that includes irreversible changes because of a large variety of endogenous and environmental factors. Paternal aging also causes genetic and epigenetic changes in spermatozoa that damage male reproductive functions through adverse effects on sperm quality and count, as well as on sexual organs and also on the hypothalamic-pituitary testicular axis. If on one hand, hormone production, spermatogenesis, and testes undergo changes as a man ages, on the other hand, the offspring of older fathers show high prevalence of genetic abnormalities, childhood cancers, and several disorders. Information on the impact of age on male fertility is of growing importance, therefore, further studies should investigate the onset of changes in the reproductive function and its effects on aging men. The aim of this chapter is to briefly discuss the effects of aging on the male reproductive system and function.
Keywords: Aging, Epigenetics, Infertility, Late-onset hypogonadism, Male fertility, Oxidative stress, Paternal age, Replacement therapy, Semen parameters, Spermatogenesis, Spermatozoa, Testes, Testosterone.