Men start to experience some definite changes in their sexuality as they approach middle age, although this is not as obvious and does not occur at such a predictable time as the female menopause. Testosterone production continues to decline, and the testes become smaller. By age 40, most men begin to notice a decrease in their sexual responsiveness and functioning. There is considerable variability, but at this life stage males are, on average, only half as sexually active as they were at their sexual peak in their late teens and early twenties.
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