Why the pill may help, and replacement therapy may harm

Hormones appear to be a paradox.

Studies have shown that birth control pills may help a woman's health, but hormone-replacement therapy proved dangerous enough to shut down one arm of the giant Women's Health Initiative study.

These seemingly conflicting findings have to do with timing, experts say.

If hormones are taken before menopause and the onset of cardiovascular problems, they appear to protect. But if taken once menopause has begun and heart trouble has started, those same hormones can harm, researchers say.

One study found that women on the pill had an 8 percent lower risk of cardiovascular disease and a 7 percent decreased risk of developing any form of cancer. The protective effect seemed to increase with time, with women who had taken birth control pills for eight or more years having a 42 percent lower risk of ovarian cancer and a 30 percent lower risk of uterine cancer.

"We believe we are among the first to show a reduction," lead author Dr. Rahi Victory, a fellow in the reproductive endocrinology and infertility program at Wayne State University School of Medicine in Detroit, told HealthDay .

The hormone-replacement arm of the WHI found that the risk of heart attack, stroke, blood clots and breast cancer among postmenopausal women taking estrogen plus progestin increased -- and Victory indicated that the latest findings do not conflict with that.

"It was a bit surprising, but it really shouldn't be," Victory said. "There's good evidence to indicate that when you expose women to estrogen in the premenopausal years, it's likely protective. There is molecular and animal evidence to indicate that estrogen can have benefits if there is no existing cardiovascular disease."

In postmenopausal women, on the other hand, estrogen may aggravate existing heart disease. "Younger women tend not to have existing heart disease, which may allow the estrogens to have a beneficial effect, rather than a detrimental one," Victory explained.

The types of hormones also factor into the equation.

"The oral contraceptives and HRT are completely different," Victory said. "They have different formulations, different dosages, and widely varying progestin compounds."

Even the researchers, however, advise keeping the findings in perspective.

"We think oral contraceptives are a safe thing to take," Victory said. "Can you say definitively that they are beneficial? No."

The bottom line, he said, is that it's important not to confuse these findings with previous findings from the WHI.

"HRT has definitively been shown to have risks in women who start it after being menopausal," Victory said. "We support the findings of the WHI and agree with them entirely. Our study suggests that oral contraceptives are likely safe and may be beneficial, but we are not recommending women take oral contraceptives to prevent heart disease and cancer because that requires a study that can demonstrate causation, such as a randomized controlled trial."

But that may never happen.