The decision whether or not to use hormone therapy to relieve menopausal symptoms just got a bit more complex.

For some menopausal women, taking a combination of estrogen and progesterone (or estrogen alone for women who have had hysterectomies) is the only way to get relief from sleep-disrupting night sweats and hot flashes. But they're also warned about the increased risk of breast cancer associated with hormone use -- a risk that becomes significant after women have been on hormones for more than five years.

Now a new study published today in the Journal of the American Medical Association shows an association between hormone use and ovarian cancer -- and it kicks in almost immediately after women begin taking hormones.

In the study, which culled the health records of nearly 1 million Danish women, researchers found a 38 percent greater risk of ovarian cancer among women who were currently taking hormone therapy. The risks didn't appear to be affected by the typesof hormones women were taking, the dose, the duration, or whether they were taking estrogen alone or a combination of estrogen and progesterone.

Women who previously took hormones, however, can rest easy: "Our data suggests their risk of ovarian cancer is similar to never users after two years cessation," writes study author Lina Morch, an epidemiologist at Copenhagen University, via E-mail.

What's more, the actual increased risk of ovarian cancer is very low.

The study found one additional ovarian cancer for every 8,300 women taking hormone therapy each year. That comes out to about 140 extra cases of ovarian cancer in Denmark over the study period of eight years. Still, "even one case of cancer is one case too many," says Isaac Schiff, chief of obstetrics and gynecology at Massachusetts General Hospital in Boston, who is familiar with the study. He said the statistical association was weak but probably real. (Previous research has also found a link between hormones and ovarian cancer.)

Unknown, though, is whether taking hormones can actually trigger ovarian cancer.

"Women who take hormone therapy tend to be monitored more closely by their doctors," he explains, "so diagnoses of ovarian cancer may be made more frequently in this group."

The big question: Just how much should this latest news factor into a woman's decision about taking hormones?

Morch tells me that it should weigh in pretty considerably. "Ovarian cancer is highly fatal, so accordingly this risk warrants consideration when deciding whether to use HT," she writes in her E-mail.

Women with a family history of ovarian cancer, in particular, should consider not taking hormones, she adds. Unfortunately, bioidentical hormones -- which have been touted by some as safer than traditional hormone therapy--are associated with the same increased ovarian cancer risk. Women in the Danish study all took estradiol, a bioidentical hormone that has the same chemical structure as estrogen made by the body. And there was no difference in cancer risk between women who took non-identical synthetic progestin and those who took bioidentical progesterone.

Schiff says heightened caution may be unnecessary.

Because there's still no proof that hormones cause ovarian cancer, "I personally won't change what I tell my patients," he says. "When I prescribe hormones, the major cancer I discuss is breast cancer. I also mention endometrial cancer and how that risk can be lowered by taking progesterone along with estrogen."

He tells women that there's "controversial" evidence suggesting that hormones may also increase the risk of ovarian cancer but that the increased risks are "extremely low."

While someone with a family history of ovarian cancer may understandably want to skip hormone therapy, he says it's not necessary based on the results of this study or the previous ones.

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