If you've been diagnosed with breast cancer or have tested positive for an abnormal breast cancer gene ( BRCA1 or BRCA2 ) and so are at high risk, you shouldn't use HRT. The hormones in HRT can cause hormone-receptor-positive breast cancers to develop and grow. While only a few small studies have looked at HRT use in women with a personal history of breast cancer, the fact that HRT use increases breast cancer risk among women in general makes almost all doctors advise women with a personal history of breast cancer to avoid HRT. The prescribing sheet included with HRT clearly states that it is "contraindicated in women with a diagnosis of breast cancer." Not being able to use HRT can present a challenge for many women. If you're having severe hot flashes or other menopausal side effects and have a personal history of breast cancer, talk to your doctor about non-hormonal options, such as dietary changes, exercise, weight management, acupuncture, or meditation.
HRT has been shown to have other beneficial effects. In a study women taking estrogen through HRT showed that the estrogen positively affects the prefrontal cortex by boosting the working memory. This suggests that estrogen may play a key role in certain frontal lobe functions in women.  Women using HRT after menopause have no additional weight gain compared to women who do not use HRT.  Also women who use HRT with an estrogen component show positive effects in their sex life (mainly increasing their sex drive and sexual sensitivity) but the effects are inconsistent across women. These sexual improvements may dissipate after receiving some forms of HRT for extended periods of time.