Hormone replacement therapy

Hormone replacement therapy (HRT), also known as menopausal hormone therapy or postmenopausal hormone therapy, is a form of hormone therapy used to treat symptoms associated with female menopause.^[1][2] Effects of menopause can include symptoms such as hot flashes, accelerated skin aging, vaginal dryness, decreased muscle mass, and complications such as osteoporosis (bone loss), sexual dysfunction, and vaginal atrophy. They are mostly caused by low levels of female sex hormones (e.g. estrogens) that occur during menopause.^[1][2]

Estrogens and progestogens are the main hormone drugs used in HRT. Progesterone is the main female sex hormone that occurs naturally and is also manufactured into a drug that is used in menopausal hormone therapy.^[1] Although both classes of hormones can have symptomatic benefit, progestogen is specifically added to estrogen regimens, unless the uterus has been removed, to avoid the increased risk of endometrial cancer. Unopposed estrogen therapy promotes endometrial hyperplasia and increases the risk of cancer, while progestogen reduces this risk.^[3][4] Androgens like testosterone are sometimes used as well.^[5] HRT is available through a variety of different routes.^[1][2]

The long-term effects of HRT on most organ systems vary by age and time since the last physiological exposure to hormones, and there can be large differences in individual regimens, factors which have made analyzing effects difficult.^[6] The Women's Health Initiative (WHI) is an ongoing study of over 27,000 women that began in 1991, with the most recent analyses suggesting that, when initiated within 10 years of menopause, HRT reduces all-cause mortality and risks of coronary disease, osteoporosis, and dementia; after 10 years the beneficial effects on mortality and coronary heart disease are no longer apparent, though there are decreased risks of hip and vertebral fractures and an increased risk of venous thromboembolism when taken orally.^[7][8]

"Bioidentical" hormone replacement is a development in the 21st century and uses manufactured compounds with "exactly the same chemical and molecular structure as hormones that are produced in the human body."^[9] These are mainly steroids derived from plants^[10] and can be a component of either registered pharmaceutical or custom-made compounded preparations, with the latter generally not recommended by regulatory bodies due to their lack of standardization and formal oversight.^[11] Bioidentical hormone replacement has inadequate clinical research to determine its safety and efficacy as of 2017.^[12]

The current indications for use from the United States Food and Drug Administration (FDA) include short-term treatment of menopausal symptoms, such as vasomotor hot flashes or vaginal atrophy, and prevention of osteoporosis.^[13]