Hormone replacement therapy: review, update, and remaining questions after the Women's Health Initiative Study.

Hormone replacement therapy (HRT) is a collective term to include a variety of sex steroids, estrogens, and progestogens, given to postmenopausal women at various doses and administered through various routes. HRT is used for the relief of menopausal symptoms, with many women experiencing considerable improvement in their quality of life. It is also used for the prevention and treatment of osteoporosis, which is as effective as other available therapies. Other potential benefits of HRT are the prevention of cardiovascular disease and dementia. The main risks of HRT are an increased incidence of breast cancer and a transient increase in venous thromboembolism. The Women's Health Initiative is the largest randomized clinical trial of HRT to date, and has demonstrated benefits and risks of one specific HRT regimen. Skeletal benefits have been confirmed in terms of fracture reduction, as has a small risk of breast cancer development. Further studies of other HRT regimens are urgently required to clarify the cardiovascular effects.