what is the most significant risk factor for endometrial ca?
['Obesity.', 'Things that affect hormone levels, like taking estrogen after menopause, birth control pills, or tamoxifen; the number of menstrual cycles (over a lifetime), pregnancy, certain ovarian tumors, and polycystic ovarian syndrome (PCOS)', 'Use of an intrauterine device (IUD)', 'Age.', 'Diet and exercise.', 'Type 2 diabetes.']