In July, women and their doctors were surprised to learn that investigators for the Women's Heath Initiative (WHI) unexpectedly halted one portion of the study — the trial of estrogen and progestin versus a placebo in healthy postmenopausal women. Five years into the eight-year study, the researchers found that the risks outweighed the benefits. They felt they had to stop the trial.

Many women now taking combined hormone replacement therapy (HRT) don't know what to do. As I help my own patients decide whether or not to continue, we consider the following questions.

Are the study results valid? The WHI findings are significant. The study involved more than 16,000 women without heart disease and is the largest clinical trial of HRT thus far. The estrogen plus progestin study was designed to assess the health benefits and risks of the most commonly used form of HRT in the United States. Half of the participants received Prempro (0.625 mg of conjugated equine estrogens and 2.5 mg of medroxyprogesterone acetate) and half got a placebo.

The most surprising finding was an increase in heart attacks and stroke in healthy women. Research prior to the start of the WHI had suggested the opposite might occur. The incidence of breast cancer and blood clots also increased in the treatment group — a not wholly unexpected result. The study did detect some benefits, including a reduced risk of colorectal cancer and hip fracture.

How risky is HRT? The study's results (see box, below) may seem alarming. But the absolute risk to an individual woman is relatively small. For example, in 10,000 women taking HRT for a year, there will be 7 more heart attacks, 8 more invasive breast cancers, 8 more strokes, and 8 more cases of blood clots in the lungs (pulmonary em-boli). At the same time, there will be 6 fewer colorectal cancers and 5 fewer hip fractures. Still, a treatment used in healthy women strictly for prevention shouldn't carry extra risks. estrogen progestin supplement

Do the results of the WHI apply to me? That depends. If you're a healthy woman taking HRT to prevent heart disease, the answer is definitely yes. The WHI found that long-term HRT (with Prempro) doesn't prevent cardiovascular disease; it actually increases risk.

The WHI results are not relevant to women taking HRT in the short term to relieve menopausal symptoms such as hot flashes.

These results also do not apply to women taking estrogen alone. This study cannot distinguish the effects of estrogen from those of progestin. In fact, the part of the study that is evaluating women taking only estrogen continues today.

The findings also don't tell us about the effects of lower doses of Prempro or other formulations of estrogens and progestins either taken by mouth or absorbed through the skin.

Thinking about trying a natural replacement   for your estrogen progestin supplement.

What if I'm taking HRT to reduce my risk for osteoporosis? While estrogen reduces bone loss, it's only one component of good bone health. The basics include getting enough calcium and vitamin D and getting regular weight-bearing exercise. Moreover, there are other medications to treat osteoporosis. Drugs like raloxifene benefit the bones and blood vessels. Bisphosphonates (such as alendronate) are also known to improve bone health in postmenopausal women. You might consider these options if you're inclined to discontinue HRT.

Should I stop? The WHI's results indicate that the risks of HRT to an individual woman are small, so you have time to figure out what's best for you. Stay informed about the effects of HRT and know why you're taking it.

If you're taking HRT to prevent heart disease, you should discontinue it. Maintain a heart-healthy lifestyle and talk to your doctor about aspirin therapy and other medications, such as statins, proven to protect heart health.

If you've been taking HRT for less than five years to relieve menopausal symptoms or treat osteoporosis, you're okay for the time being. After five years, you'll need to weigh the benefits of symptom relief, bone health, and a reduced risk of colorectal cancer against the increased risk of invasive breast cancer. As always, this will be an individual decision.

We'll know more as scientists evaluate the details of the WHI data. You can reassess your situation with your doctor at any time and can always change your mind.