Which factor increases the risk of endometrial cancer?

Endometrial cancer is most closely associated with prolonged exposure to estrogen, particularly when that estrogen is not opposed by progesterone. Obesity plays a significant role in this risk because adipose tissue can produce estrogen. In an environment of excess estrogen—whether due to obesity, age, or other hormonal factors—the endometrial lining can undergo hyperplasia, which increases the likelihood of developing cancer.

Obesity not only increases estrogen production but also disrupts the balance of reproductive hormones, resulting in a high estrogen-to-progesterone ratio. This unopposed estrogen exposure can lead to abnormal endometrial growth and potentially progress to malignancy. Therefore, the combination of obesity and prolonged estrogen exposure represents a well-established risk factor for the development of endometrial cancer, making it the correct answer.

In contrast, high physical activity levels are generally associated with a lower risk of many cancers, including endometrial cancer. Regular menstrual cycles suggest a more balanced hormonal environment with cyclical progesterone exposure, which can be protective against endometrial cancer. A younger age at menarche typically does not increase cancer risk; instead, factors like early menarche often correlate with longer reproductive lifespan, which is more about cumulative exposure rather than enhancing immediate risk