What is a natural reason for amenorrhea in women?

Menopause is a natural biological process that marks the end of a woman's reproductive years, typically occurring in their late 40s to early 50s. During this stage, the body's production of hormones like estrogen and progesterone significantly decreases, leading to the cessation of menstruation. This is a normal part of aging and signifies that the ovaries have stopped releasing eggs, thus resulting in amenorrhea.

While excessive exercise, medication, and low body weight can also lead to amenorrhea, they are not inherent biological processes like menopause. Instead, they represent lifestyle or health-related factors that can disrupt the regular menstrual cycle. Menopause stands out as a natural transition every woman will experience, making it the most fitting answer in this context.