Healthy, active men experience a slight decline in testosterone levels as they age; however, they also develop a higher density of androgen receptors, which enhances the effectiveness of the testosterone they have. This means that older men can still build muscle effectively if they maintain a healthy lifestyle. Interestingly, testosterone is also crucial for women, and low levels can lead to similar effects as in men. Age may influence hormone levels, but with the right approach to diet and exercise, individuals can mitigate its impact.