Hormone therapy alleviates symptoms of menopause, but fear of an increased risk of breast cancer deters some women and physicians from its use. Research has shown, though, that not all hormone replacement regimens have the same outcome. An editorial in Case Reports in Women’s Health is an excellent summary of this research based on data from hundreds of thousands of women.
The use of estrogen in hormone replacement therapy has a very low increased risk of breast cancer, but has positive effects on osteoporosis and may prevent cardiovascular disease when initiated at or shortly after menopause. To put this into perspective, the risk associated with long-term estrogen use is much lower than the risk conferred by obesity, inactivity, and alcohol use. The main increased risk of breast cancer from hormone therapy derives from progestins in the estrogen-progesterone regimen. Several different progestins are commonly used, and research has shown that among synthetic progestins, medroxyprogesterone acetate, levonorgestrel, and norethisterone have a higher risk of breast cancer while dydrogesterone has a lower risk in long-term use. Additionally, we know that bio-identical progesterone (micronized progesterone) does not increase breast cancer when used for no more than five years (see this 2018 article). Dydrogesterone or micronized progesterone are the best choice for hormone therapy when breast cancer is a concern.
Hormone therapy at menopause should be tailored to the individual. Arm yourself with accurate information about the impacts of specific hormones when you talk to your doctor.