While the back-and-forth over the risks and benefits of hormone-replacement therapy at menopause is enough to give women whiplash, each study is providing doctors with a better idea of exactly how — and when — supplemental hormones can help. The latest analysis of data from the Women's Health Initiative shows that women who have had a hysterectomy and use estrogen-only therapy have less buildup of calcium plaques in their arteries than women who don't use the hormone. Not only does estrogen not hurt the heart, this study suggests, it may help it — at least for younger women, ages 50-59.