Many women know that hormone replacement therapy (HRT), while associated with many benefits, can pose some health risks in certain women. HRT received much attention after two large government studies, the Women’s Health Initiative (WHI) trials, were halted after an increase in heart problems thought to be linked to HRT.

But there’s also been interest in HRT’s beneficial role in other aspects of health, whether it might help prevent certain chronic diseases like osteoporosis and post-menopausal problems like pain during sex

A new study looked at data from the WHI trials, following over 27,000 postmenopausal women after the studies had stopped. Some of the women, who had not had hysterectomies, were on an estrogen plus progesterone, known as CEE, plus medroxyprogesterone acetate (MPA). Other women, who did have hysterectomies, were on CEE alone.

Women on this treatment had increased risk for coronary heart disease, breast cancer, stroke, pulmonary embolism, dementia (in women over 65), gallbladder disease, and urinary incontinence.

The women were all between 50 and 79 when the studies began in 1993. The team tracked what kinds of health issues the women encountered over several years.

In general, the risks linked to being on CEE plus MPA (in women without hysterectomy) outweighed the benefits. Women on this treatment had increased risk for coronary heart disease, breast cancer, stroke, pulmonary embolism, dementia (in women over 65), gallbladder disease, and urinary incontinence.

The majority of the health risks diminished after the HRT was stopped, but breast cancer risk remained higher.

There were some benefits, however, including decreased risk of hip fractures, diabetes, and vasomotor symptoms. And for women who had had a hysterectomy and were on only CEE, there was a better risk-benefit balance. These women were more at risk for stroke and venous thrombosis, but had a lower risk of hip and other bone fractures. Their risk of breast cancer was slightly reduced, although not at a level considered statistically significant.

The risk of death in both treatment groups was neither higher nor lower than among women in the control group.

The research team says that even though HRT may be a good option for managing “moderate to severe menopausal symptoms among generally healthy women during early menopause,” the risks are just too great to recommend using CEE for the prevention of other diseases, even among younger women.

Findings from other studies, they add, have already suggested that HRT may be less safe when it’s started later in life, given the risks for heart disease.

The bottom line is that it seems to matter when, after menopause, hormone treatment starts, as well as what kinds of hormones are used and whether the woman has had a hysterectomy or not. There’s no one answer for everyone. Again, the most recent studies suggest that HRT is safer if started sooner after menopause, rather than later, but if you have remaining questions about whether HRT is right for you, it’s always best to talk with your doctor in person.

The study was carried out by a team at Brigham and Women's Hospital and published in the Journal of the American Medical Association.