Administration of sex hormones to women after menopause or oophorectomy. Syn: hormone replacement therapy.
In the later decades of the 20th century, estrogen replacement therapy became a standard practice for the prevention of cardiovascular disease and osteoporosis in postmenopausal women. During the 1980s, recognition that administration of unopposed estrogen increases the risk of endometrial cancer led to the addition of progestogen to postmenopausal regimens. In 2000, at least one third of American women between the ages of 50 and 75 were taking estrogenic hormones. The notion that estrogen replacement therapy, widely used to combat menopausal symptoms such as atrophic vaginitis and vasomotor instability (“hot flashes”), might also protect against cardiovascular disease arose partly from the statistical observation that a woman's risk of adverse cardiovascular events increases rapidly after menopause. But although numerous observational studies previously seemed to confirm this protective role of hormones, large and powerful clinical trials later demonstrated not only a lack of benefit from estrogen administration but actually an increased risk of coronary artery disease, stroke, pulmonary embolism, invasive breast cancer, and Alzheimer dementia. Administration of estrogen after natural or surgical menopause remains an effective measure against vasomotor instability and atrophic vaginitis; raises HDL cholesterol; lowers levels of total and LDL cholesterol, apolipoprotein B, lipoprotein Lp(a), homocysteine, fibrinogen, and renin, and reduces the risk of osteoporosis and colorectal cancer. It is also used for palliation in selected patients with breast and prostatic cancer. However, it is no longer endorsed as prophylaxis against cardiovascular disease in postmenopausal women, because the risk of adverse effects appears to outweigh expected benefits for most women. Although estrogen therapy helps prevent bone loss after menopause, evidence is lacking that it reduces the risk of fractures. Moreover, anecdotal reports that estrogen may retard the onset and progression of Type 2 diabetes mellitus, parkinsonism, and Alzheimer dementia lack firm experimental support. In fact, the Women's Health Initiative Memory Study found that estrogen plus progestogen therapy slightly increases the risk of dementia. Postmenopausal women with established cardiovascular disease who take estrogen experience about a threefold increase in the risk of venous thromboembolism. Women with a history of prior ischemic stroke who take estrogen have an increased risk of subsequent fatal stroke. Postmenopausal women who take estrogen have a 40% increase in the risk of gallbladder disease. Several studies have indicated an increased incidence of carcinoma of the breast, ovary, and endometrium. Combining cyclic progestogen administration with daily estrogen restores menstrual cycles (when the uterus is intact) but apparently does not reduce the risk of carcinogenesis, and may even increase it. In addition, current studies suggest that estrogen alone is less likely than estrogen-progestogen to cause adverse cardiovascular effects.
Reference: Stedman's Medical Dictionary