A woman’s menstrual cycle is controlled by the hormones estrogen and progesterone circulating in their bloodstream. As women enter into their 40s and 50s these levels start to decline and she begins to develop the symptoms of peri-menopause or menopause. These symptoms include hot flashes (flushing), insomnia, bone changes, a lack of a menstrual period and unwanted aging. Hormone replacement therapy, most commonly done with synthetic estrogen and progesterone, is the most effective treatment for vasomotor symptoms (flushing) and other symptoms of menopause. However, there are important distinctions that must be made between taking estrogen plus progestin and estrogen alone in terms of benefits and risks. Conventional wisdom prior to.