Final answer:
Men experience decreased testosterone production due to declining Leydig cell activity as they age, often starting between 40 to 50, leading to symptoms of andropause and can result in reduced sperm quality, quantity, and motility.
Step-by-step explanation:
The correct option is B:
The reproductive change that men experience as they age is b) Decreased testosterone production. This condition, often referred to as andropause or male menopause, is characterized by a decline in Leydig cell activity usually beginning between 40 to 50 years of age. This decline in testosterone levels can lead to symptoms such as fatigue, reduced muscle mass, depression, and loss of libido. Additionally, there is a reduction in spermatogenesis, resulting in lowered fertility.
As a result, there's a reduction in circulating testosterone concentrations, which can lead to various symptoms including fatigue, reduced muscle mass, depression, anxiety, mood swings, loss of libido, and sexual dysfunction. Although a severe decline in testosterone rarely affects sperm production until very old age, a reduction in spermatogenesis resulting in lowered fertility is possible. Moreover, the quality, quantity, and motility of sperm are often reduced in older men.