Dr. Christiane Northrup on the history of hormone replacement therapy.

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Many women find the specifics of hormone replacement therapy confusing, and Dr. Northrup says it's no surprise. "The mainstream medical community has flip-flopped on hormone replacement over the last five decades," she says. "It's good for you; it's bad for you. It's no wonder women are confused."

A lot of it is controversial because previous studies have linked some kinds of hormone replacement therapy with cancer, heart attacks and strokes. 

Watch Dr. Northrup explain the history of hormone therapy. Watch