Fertility and Sperm Quality in the Aging Male.

Parenthood at an older age is becoming a trend among men, especially in the most developed societies. Aging has a significant impact on male fertility. Older men exhibit notable disturbances in the reproductive axis, with steroidogenesis being impacted much more than spermatogenesis. The endocrine changes, together with morphological and functional alternations of the aging testis, result in decreased testosterone production. Nonetheless, studies are needed to scrutinize the impact of age per se versus age-induced dysfunction of the reproductive axis. Furthermore, the multiple effects of aging on the acquisition of sperm motility, on sperm morphology and concentration indicate that the quality of spermatozoa declines over time, but few works have shed light on the molecular mechanisms that hamper sperm function in old men. In fact, this question is far from being completely answered and this is a subject of controversy. Hence, we will present an up-to-date review and discuss the molecular mechanisms involved in the alteration of the reproductive function in aging men. We will focus on the functioning of the reproductive axis and what are the major effects of aging in spermatogenesis. We will also discuss how aging affects sperm quality and possible causes underlying sperm dysfunction with special emphasis in oxidative stress.