What is HRT?
HRT, or hormone replacement therapy, is used by people who are going through menopause or who have already been through it. Before menopause, the ovaries make 2 female hormones: estrogen and progestin. With menopause, a natural life stage for menstruating people, the ovaries stop producing these female hormones. This can lead to symptoms of menopause, including hot flashes, night sweats, mood swings, trouble sleeping, vaginal dryness and urinary incontinence (difficulty holding urine). HRT is used to replace estrogen and progestin and relieve the symptoms of menopause.
There are many different types of HRT. Most people receive both estrogen and progestin. Because estrogen can increase the risk of endometrial cancer (cancer of the lining of the uterus), progestin is taken to offset this risk. However, people without a uterus (i.e., those who have had a hysterectomy) do not need to take progestin. There are different types of estrogen (such as conjugated estrogen, estropipate, and estradiol) and progestin (such as medroxyprogesterone acetate and micronized progesterone). There is also a large variety of dosage forms (such as tablets, patches, creams, and vaginal rings).
At one time, HRT was also used to prevent heart disease. The results of the Women’s Health Initiative (WHI) Study, a major US study that examined the risks and benefits of HRT in over 16,000 participants, have raised some concerns about the long-term safety of HRT. To date, it remains the largest, randomized clinical study on this question.
The study found that use of one type of HRT for more than 5 years led to increased risks of heart disease, breast cancer, stroke, and venous thromboembolism (a serious condition where blood clots break loose and lodge in the veins of the leg or the lung). HRT was also found to decrease the risk of osteoporosis and colorectal cancer. As a result of this study, HRT is no longer recommended for the prevention of heart disease.
It is important to note that not all forms of HRT have been linked to an increased risk and that these risks occurred with long-term versus short-term usage. Details are discussed below. If you are taking HRT or thinking of starting it, talk to your doctor about the benefits and risks.
What was the study about, and what does it mean for Canadians taking or considering taking HRT?
The Women’s Health Initiative (WHI) Study looked at the benefits and risks of HRT in a large group of Americans. Over 16,000 healthy postmenopausal individuals aged 50 to 79 were enrolled in the study. These people were randomly assigned to one of 2 groups:
- Treatment group: People in this group received estrogen (conjugated equine estrogen 0.625 mg) and progestin (medroxyprogesterone acetate 2.5 mg) by mouth once daily. This is one of the most common forms of HRT. They took the hormones continuously, without regular monthly breaks.
- Placebo group: People in this group received a placebo (a tablet that contains no active ingredients and is designed to look like the treatment medication) by mouth once daily.
The study measured the effects of HRT on heart disease, stroke, venous thromboembolism (a serious condition where blood clots break loose and lodge in the veins of the legs or lungs), osteoporosis (bone loss), colorectal cancer, and breast cancer. The WHI planned to run the study for about 8 years but stopped it early, after only 5 years, for 2 reasons:
- An increased risk of breast cancer was found with HRT treatment as compared to placebo.
- The overall risk outweighed the benefits of HRT treatment as compared to placebo.
In women taking HRT in this study:
- heart disease risk was 29% higher
- stroke risk was 41% higher
- breast cancer risk was 26% higher
- the risk of venous thromboembolism was more than doubled
- hip fracture risk was 33% lower
- colorectal cancer risk was 37% lower
What does this mean? At first glance, these percentages seem quite high. But the risks of these conditions were very low to begin with, so the actual number of people experiencing them is still low. Every year, a group of 10,000 people taking HRT would have:
- 7 more heart attacks (37 vs. 30)
- 8 more strokes (29 vs. 21)
- 8 more cases of breast cancer (38 vs. 30)
- 18 more venous thromboembolisms (34 vs. 16)
- 5 fewer hip fractures (10 vs. 15)
- 6 fewer cases of colorectal cancer (10 vs. 16)
What did the experts say about this study?
Medical experts pointed out that the study only assessed one form of HRT. These results may not apply to people taking different estrogens or progestins, those using other dosage forms such as the estrogen patch, or those taking estrogen alone. People taking hormones in a cyclic fashion (with regular monthly breaks from hormones) may also have different HRT risks and benefits. In addition, the people in this study were 50 to 79 years of age, so the study results may not apply to people going through premature menopause (menopause before the age of 40 years).
In this study, people taking HRT were already faced with a slightly increased risk of heart attack and stroke after 2 years of treatment as compared to those taking the placebo. Their risk rose again after taking HRT for 3 years. Experts recommend that HRT should not be continued or started to prevent heart disease.
The balance of risk and benefit may be quite different for any individual, depending on their reasons for taking HRT, how long they will be taking it, and their medical history. Recent analyses of this study in combination with other smaller ones find that the degree of heart disease risk increase depends on the age that you start HRT relative to menopause. Each individual should consult their doctor to determine their own personal risks and benefits for HRT.
What should you do?
If you are already taking HRT, or thinking about starting, talk to your doctor. Depending on your reasons for taking HRT, your medical history and the length of time that you may need to take HRT, it may still be a viable option for you. Together with your doctor, you can chart out your personal risks and benefits and choose the most appropriate therapy. The Society of Obstetricians and Gynecologists of Canada (SOGC) recommends that people meet with their doctors at least once a year to re-evaluate whether they still need HRT. Your doctor may also be able to recommend alternatives to HRT.
All material copyright MediResource Inc. 1996 – 2025. Terms and conditions of use. The contents herein are for informational purposes only. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Source: www.medbroadcast.com/healthfeature/gethealthfeature/Hormone-Replacement-Therapy