Combination Hormone Therapy Offers Greater Benefit for Postmenopausal Women

From the WebMD Archives

Nov. 17, 1999 (Atlanta) -- Uterine bleeding caused by estrogen replacement in postmenopausal women decreased when a second sex hormone was added to hormone replacement therapy (HRT), according to a study in a recent issue of Obstetrics and Gynecology.

The study supports current science recognizing that the addition of progestin (a synthetic form of the sex hormone progesterone) to estrogen for HRT reduces uterine bleeding by blocking the tendency of the lining of the uterus (endometrium) to thicken during HRT.

But the study also suggests that bleeding caused by estrogen-only replacement may only occur in women predisposed to bleeding -- in other words, that replacement therapy alone will not always cause bleeding.

But if bleeding does occur, "there is clearly an increased risk of cancer of the lining of the uterus if estrogen is taken without progestin," William Andrews, MD, past president of the American College of Obstetricians and Gynecologists, tells WebMD.

Starting estrogen-only replacement therapy in some postmenopausal women prompts bleeding as the hormone reintroduces menstruation. Estrogen replacement therapy is used to treat the hot flashes and vaginal dryness of menopause and to protect against osteoarthritis and heart disease -- a function of natural estrogen in premenopausal women.

The researchers divided 1,175 postmenopausal women into groups receiving estrogen pills alone or estrogen pills in combination with progestin at three different dosage strengths. The average age of the participants was 57.

Results of the study showed that nearly 30% of women in the combination therapy group experienced bleeding during the first three months of therapy, but this was reduced to 10-20% at the end of one year.

In the estrogen-only group, after one year, 25% had experienced bleeding, which usually tapered off over time.

"Most patients take estrogen every day and have 12-14 days of progestin cycled in," says Andrews, professor emeritus of obstetrics and gynecology at Eastern Virginia Medical School in Norfolk. "The idea is that during the first few years, patients will have irregular bleeding. The combination works better if therapy begins after several years of menopause. For the first several years, patients are put on a cycle, then switched to the two combined."

Overall, the study found that 50% of the entire patient population experienced uterine bleeding no matter which hormone replacement regimen was used.

The researchers write that, "This finding suggests that the risk of a woman bleeding during [hormone replacement therapy] might reflect, in part, an individual predisposition to bleed."

Like Andrews, the study researchers report that bleeding is more likely to occur when HRT begins during the first few years after menopause.