What is a notable change in the male reproductive system with aging?

With aging, one of the notable changes in the male reproductive system is a decrease in testosterone levels. This condition, often referred to as andropause, is characterized by a gradual decline in testosterone production that typically begins in middle age. Testosterone levels can diminish by approximately 1% per year after the age of 30 or 40.

This decrease can lead to various symptoms, including reduced libido, erectile dysfunction, decreased muscle mass, and increased body fat. The physiological rationale behind this decline includes testicular dysfunction, alterations in the hypothalamic-pituitary-gonadal axis, and a reduction in the number of Leydig cells in the testes, which are the primary producers of testosterone.

The other choices do not accurately reflect typical changes associated with aging. For instance, testosterone production does not increase with age; rather, it declines. Testicular hypertrophy is not a common occurrence and, in fact, atrophy or a decrease in testicular size can occur over time. Finally, fertility generally decreases with aging in men, primarily due to lower testosterone levels and lower sperm quality, not an increase in fertility. Therefore, the marked reduction in testosterone is a significant and well-documented change in the male reproductive system as men age.