Hormone therapy: The risk-benefit tightrope.(Women's Health Initiative)

Women must balance heart disease protection and breast cancer risk.

It was a shock several years ago when results from a large, government-funded study called the Women's Health Initiative (WHI) showed that postmenopausal women who took hormones were more likely to have heart problems than those who didn't. Previous research had pointed to both risks and benefits from hormone therapy. The risks? Stroke, blood clots in the veins that could potentially travel to the lungs (pulmonary emboli), and most of all, breast cancer -- all were more likely with hormone therapy.

But on the benefit side of the equation were a lower risk for colon cancer, protection against broken bones, relief from a variety of postmenopausal symptoms like hot flashes and night sweats -- and protection against heart disease. And since heart disease is by far the most common cause of both death and disability in women, protection against heart disease was important.

But the 2002 WHI results threw the risk-benefit balancing act out of alignment. It seemed that hormone therapy increased the risk for both the most feared disease, breast cancer, and the most common one, heart disease.

By the end of 2002, the use of hormone therapy by women had plummeted by 38%, and in 2003, 20 million fewer prescriptions for hormone therapy were written. The era of widespread use of hormones by postmenopausal women was declared over.

Heart disease: Is it all in the timing?

Over the past several years, a more nuanced view of the heart disease risk from hormone therapy has emerged. Of course, it was never a secret, but researchers reconsidering the WHI results have pointed out that the average age of the women at the start of the study was 63. That means many of them started taking hormones a decade after they stopped menstruating. The usual practice is to start hormone therapy at the time of menopause when menopausal symptoms begin. For American women, on average, menopause occurs at age 51. Some experts argued that the WHI results were likely true for women in their 60s and 70s and could be misleading if applied to younger women entering menopause.