Barbra Streisand is the winner of multiple Academy Awards, Grammys, Emmys, and a Tony—and is the only performer in history to have No. 1 selling albums in six decades.

But at the Fortune Most Powerful Women Summit on Tuesday, she used her iconic voice in a somewhat unexpected way: to bring attention to women’s heart health. Streisand told the Summit crowd how the inequality in the way women and men were being diagnosed and treated for heart disease led her to co-found the Women’s Heart Alliance.

“It was once thought to be a man’s disease, but it’s become a woman’s epidemic now,” she said. Streisand noted that heart disease is the No. 1 killer of women around the world, and that it kills more women than all cancers combined. And yet over the last 50 years, the research has primarily been done on men.

“Women have different physiology, different plumbing,” she said. “We have children, we feed children. We have smaller hearts, smaller valves, smaller vascular systems.”

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That requires specific analysis, she added, because heart disease presents itself differently in women than in men. However, she said that some researchers she’d talked to only use male mice. Streisand was told female mice were too expensive, complex, and have hormones. “Duh. We have hormones. We are different,” she said. “That is an unacceptable answer.”

Symptoms of heart attacks in women are likely to show up as fatigue, nausea, and jaw pain. “Yet when they go to the ER with something they think is heartburn, they’ll be sent home with antacid or told it’s stress,” Streisand said.

She said that her organization’s lead doctor tells women they should lie and say they have chest and left arm pain—the symptoms that typically show up in men. Since doctors aren’t taught in most medical schools the differences between men’s and women’s hearts, “we’re operating in the dark,” Streisand says. “It’s staggering to me.”

Streisand, who is 74, recently had an EKG herself among other medical tests before heading on tour. “I didn’t know if I could do it, if I had the stamina,” she said. Once she got a clean bill of health, she sang 22 songs for the first time her opening night in Los Angeles.