"Another apparently paradoxical finding is that estrogenandprogestin impart a small increase in the risks for developing and dying from breast cancer, whereas estrogen alone appears to slightly reduce these risks, " according to the U.S. Preventive Services Task Force document outlining the draft recommendations.
Data from the Women's Health Initiative and other large-scale trials suggest estrogen plus progestin therapy moderately reduces risk for fractures but increases the chance of developing strokes, dementia, deep vein thrombosis, urinary incontinence and gallbladder disease.