Impact of conventional and bioidentical hormone replacement therapy on cardiovascular & breast health: A review

Several large studies demonstrated increased cardiovascular and breast cancer risks with conventional hormone therapy. Bioidentical hormone replacement therapy is thought to be a safer alternative to conventional hormone therapy. The objective of this review was to compare the cardiovascular and breast cancer risks associated with conventional hormone therapy and bioidentical hormone replacement therapy. Pubmed/MEDLINE was used to search studies published in English between 1995 and 2010. Articles were narrowed to clinical and randomized controlled trials in human females and were selected based on relevancy to cardiovascular or breast cancer risks in either conventional hormone therapy or bioidentical hormone replacement therapy. Large randomized controlled trials documented increased coronary heart disease events with conjugated estrogens plus medroxyprogesterone acetate. Some trials suggest that conjugated estrogens monotherapy may provide coronary heart disease risk reduction if initiated soon after menopause. No studies have examined coronary heart disease events with bioidentical hormone replacement therapy; however, randomized controlled trials have demonstrated that estradiol beneficially improves lipoproteins, carbohydrate metabolism, and vascular reactivity, decreases carotid intima media thickness, and slows the progression of subclinical atherosclerosis. Progesterone does not interfere with these beneficial effects. Other randomized controlled trials have documented increased breast cancer risk with conjugated estrogens + medroxyprogesterone acetate; conjugated estrogen monotherapy has not been associated with an increased risk. Smaller randomized control trials and observational studies demonstrated that estradiol induces breast epithelial proliferation; however, crystalline progesterone decreases breast proliferation and decreases breast cancer risk compared to that of hormone therapy never users. Conjugated estrogens + medroxyprogesterone acetate is detrimental to cardiovascular and breast health. Conjugated estrogens monotherapy appears to be cardiovascular and breast neutral, particularly if initiated soon after menopause. Estradiol improves cardiovascular markers but may induce breast epithelial proliferation if administered without progesterone.