Specific types of hormone replacement include:
Estrogens – bioidentical estrogens like estradiol and estriol, animal-derived estrogens like conjugated estrogens (CEEs), and synthetic estrogens like ethinylestradiol
Progestogens – bioidentical progesterone, and progestins (synthetic progestogens) like medroxyprogesterone acetate (MPA), norethisterone, and dydrogesterone
Androgens – bioidentical testosterone and dehydroepiandrosterone (DHEA), and synthetic anabolic steroids like methyltestosterone and nandrolone decanoateTibolone – a synthetic medication available in Europe but not the United States– is more effective than placebo but less effective than combination hormone therapy in postmenopausal women. It may have a decreased risk of breast and colorectal cancer, though conversely it can be associated with vaginal bleeding, endometrial cancer, and increase the risk of stroke in women over age 60 years.Vaginal estrogen can improve local atrophy and dryness, with fewer systemic effects than estrogens delivered by other routes. Sometimes an androgen, generally testosterone, can be added to treat diminished libido. Continuous versus cyclic
Dosage is often varied cyclically to more closely mimic the ovarian hormone cycle, with estrogens taken daily and progestogens taken for about two weeks every month or every other month, a schedule referred to as cyclic or sequentially combined. Alternatively, continuous combined HRT can be given with a constant daily hormonal dosage. Continuous combined HRT is associated with less complex endometrial hyerplasia than cyclic. Impact on breast density appears to be similar in both regimen timings.
This inconsistency of effect has been suggested to imply a lack of meaningful impact of HRT on breast cancer risk.There is a non-statistically significant increased rate of breast cancer for hormone replacement therapy with synthetic progesterone. The risk may be reduced with bioidentical progesterone, though the only prospective study that suggested this was underpowered due to the rarity of breast cancer in the control population. There have been no randomized controlled trials as of 2018. The relative risk of breast cancer also varies depending on the interval between menopause and HRT and route of synthetic progestin administration.The most recent follow up of the Womens Health Initiative participants demonstrated a lower incidence of breast cancer in post-hysterectomy participants taking equine estrogen alone, though the relative risk was increased if estrogen was taken with medroxy-progesterone. Estrogen is usually only given alone in the setting of a hysterectomy due to the increased risk of vaginal bleeding and uterine cancer with unopposed estrogen.HRT has been more strongly associated with risk of breast cancer in women with lower body mass indices (BMIs). No breast cancer association has been found with BMIs of over 25.