Study finds estrogen-only HRT lowers breast cancer risk, but combination HRT raises it.

A new study involving 459,476 women aged 16 to 54 found that while estrogen-only hormone replacement therapy (HRT) reduces the risk of breast cancer by 14%, HRT that includes both estrogen and progestin increases the risk by 10%. This research provides new guidance for HRT use in younger women, emphasizing that though the risk is generally small, the findings can inform clinical recommendations.