Around menopause, decreases in the levels of the hormones estrogen and progesterone result in hot flashes, night sweats, mood swings, and vaginal dryness. Lower hormone levels also increase bone loss and the risk for heart disease. Postmenopausal hormone replacement therapy (HRT) consists of taking estrogen with or without progesterone. Some women take HRT to relieve the uncomfortable symptoms of menopause. Others take it to reduce the risk for osteoporosis (thinning of the bones that can lead to fractures), which is a proven effect of HRT, and some take HRT with the hope of decreasing their chances of heart disease, colon cancer, or dementia. However, the effect of HRT on these conditions has been uncertain. HRT has side effects and does appear to increase the risk for certain diseases such as stroke, blood clots, and breast cancer. It has been unclear whether the potential benefits of postmenopausal HRT to prevent some chronic conditions are worth the associated risks.