What are the risks of hormone therapy?
In the largest clinical trial to date, a combination estrogen-progestin pill (Prempro) increased the risk of certain serious conditions, including:
- Heart disease
- Stroke
- Blood clots
- Breast cancer
A related clinical trial evaluating estrogen alone (Premarin) in women who previously had a hysterectomy found no increased risk of breast cancer or heart disease. The risks of stroke and blood clots were similar to the combination therapy.
Hormone therapy, particularly estrogen combined with a progestin, can make your breasts look more dense on mammograms, making breast cancer more difficult to detect. Also, especially when taken for more than a few years, hormone therapy increases the risk of breast cancer, a finding confirmed in multiple studies of different hormone therapy combinations, not just limited to a combination estrogen-progestin pill (Prempro).
The risks of hormone therapy may vary depending on whether estrogen is given alone or with a progestin, and depending on your current age and age at menopause, the dose and type of estrogen, and other health risks such as your risks of heart and blood vessel (cardiovascular) disease, cancer risks and family medical history.
http://www.mayoclinic.org/diseases-conditions/menopause/in-depth/hormone-therapy/art-20046372
