Like estrogen in women, testosterone in men slowly declines after age 40. Some experts say this causes a condition similar to menopause, called man-o-pause, male menopause, or andropause. They suggest treating it with testosterone replacement, which restores youthful (and sexual) vitality. Critics counter that middle-age changes in men are not analgous to menopause, and warn that testosterone replacement accelerates the growth of prostate cancer.